Fix the Most Common macOS Catalina Problems

If your Mac running macOS Catalina is slow, has Wi-Fi issues, or won’t update, the fixes below address the most common problems. This guide covers troubleshooting steps for upgrade failures, battery drain, kernel panics, and more, so you can get your system running smoothly again.

Why Catalina Causes Problems

macOS Catalina (version 10.15) was a major release that introduced significant architectural changes, including the separation of the system volume and data volume, and the requirement that all software be notarized by Apple. These changes broke many older apps and caused performance issues on some Macs, especially those with traditional hard drives. Additionally, Catalina dropped support for many Macs from 2012 and earlier, so users on older hardware often experienced sluggishness and compatibility problems.

Common Catalina Problems and How to Fix Them

1. Slow Performance and High CPU Usage

Many users report that Catalina runs slower than Mojave, particularly on machines with mechanical hard drives. This is often due to Spotlight re-indexing after the upgrade, or background tasks like photo analysis and mail rebuilding.

1. Open Activity Monitor (in /Applications/Utilities) and click the CPU tab to see which processes are using the most CPU. If you see “mdworker” or “photoanalysisd,” it’s likely indexing; give it a few hours to finish.
2. If indexing seems stuck, turn off Spotlight for your main drive in System Preferences → Spotlight → Privacy, add the drive, then remove it to force a re-index.
3. For hard-drive based Macs, consider upgrading to an SSD—this makes the biggest difference in overall speed.

2. Wi-Fi Drops or Won’t Connect

Wi-Fi issues after a Catalina update are commonly caused by stale network preferences or DNS conflicts.

1. Go to System Preferences → Network, select Wi-Fi, and click the minus sign to remove it. Then click the plus sign to re-add it.
2. Delete the Wi-Fi preferences file: in Finder, press Cmd+Shift+G and type /Library/Preferences/SystemConfiguration/. Move these files to the Desktop (you’ll need to enter your password): com.apple.airport.preferences.plist, com.apple.network.identification.plist, NetworkInterfaces.plist, and preferences.plist. Restart your Mac and re-join your Wi-Fi network.
3. If the problem persists, try resetting your router or checking for a firmware update.

3. Apps Won’t Open or Are “Damaged”

Catalina requires all apps to be notarized. If you see ““app” is damaged and can’t be opened,” it’s often because the app was downloaded from the internet and Gatekeeper is blocking it.

1. Right-click (or Ctrl-click) the app in Finder and select Open. Then click Open in the dialog that appears—this bypasses Gatekeeper for that one launch.
2. If that doesn’t work, check if the app is 32-bit. Catalina only runs 64-bit apps. You can check in About This Mac → System Report → Applications; look for “64-Bit (Intel): No”.
3. If the app is truly damaged (e.g., a corrupted download), delete it and re-download from the developer’s website.

4. Battery Drains Fast on MacBooks

After upgrading to Catalina, some users notice their battery life decreases. This is often due to the “Hey Siri” feature constantly listening, or background tasks like Photos syncing.

1. Go to System Preferences → Siri and uncheck “Listen for ‘Hey Siri’”.
2. Check System Preferences → Battery to see which apps are using the most energy. Close any apps you aren’t using.
3. Reset the SMC (System Management Controller) if the issue persists—the steps vary by Mac model, but generally involve shutting down, holding Shift+Control+Option on the left side of the keyboard for 10 seconds, then turning on.

5. Kernel Panics and Random Restarts

Kernel panics (the “Your computer restarted because of a problem” message) can be caused by incompatible kexts (kernel extensions) or hardware issues.

1. Boot into Safe Mode (hold Shift at startup) to see if the panic occurs. If not, a third-party kext is likely the culprit.
2. Check System Report → Software → Extensions for any third-party kexts. Remove or update them.
3. If you installed an app that uses a kext (like some VPNs or hardware drivers), uninstall it and see if the panics stop.

6. Update Stuck or Fails to Install

If the Catalina update gets stuck on the Apple logo or fails to install, try these steps:

1. Restart your Mac and try again. Sometimes a simple reboot clears the issue.
2. Ensure you have enough free disk space—at least 20GB is recommended for the upgrade.
3. If the update fails repeatedly, download the standalone installer from the App Store (search for “Catalina”) and run it manually.

Frequently Asked Questions

Why is my Mac so slow after Catalina?

Catalina introduced a new read-only system volume that requires more disk I/O, which can slow down older Macs, especially those with hard drives. Spotlight re-indexing and other background tasks after the upgrade also contribute. Give it a day or two, and if it remains slow, consider upgrading to an SSD or downgrading to Mojave if your Mac supports it.

How do I downgrade from Catalina back to Mojave?

You can downgrade by backing up your data, then using the Recovery Mode (Cmd+R at startup) to erase your drive and reinstall macOS Mojave. You’ll need to have a Time Machine backup or use Migration Assistant to restore your files. Note that this is only possible if your Mac supports Mojave (most 2013 and later models do).

Will my old 32-bit apps work on Catalina?

No. Catalina is the last macOS version that supports 32-bit apps, but it does not run them at all—they will not open. You’ll need to find 64-bit alternatives or check if the developer has updated the app. You can check which apps are 32-bit in System Report.

Why does my Mac say “macOS cannot be installed on this computer”?

This usually means your Mac model is not supported by Catalina, or your disk is not formatted correctly. Check Apple’s list of supported models—if yours is from 2012 or earlier, it’s likely not supported. If your Mac is supported, ensure your drive is formatted as Mac OS Extended (Journaled) or APFS, and that you have enough free space.

How do I fix the “Your computer restarted because of a problem” error?

This is a kernel panic. First, note the date and time it happened. Boot into Safe Mode and see if it recurs. If not, it’s likely a third-party kernel extension or app. Check System Report for extensions and remove any that are not from Apple. If it happens randomly, it could be a hardware issue like failing RAM or a faulty logic board—contact Apple Support or an authorized service provider.

Prevention and Best Practices

To avoid these issues in the future, always back up your Mac with Time Machine before any major upgrade. Keep your apps updated to versions that are Catalina-compatible, and avoid installing unnecessary kernel extensions. If you rely on older software, consider staying on Mojave until you’re ready to upgrade your hardware. Regular maintenance, like clearing caches and ensuring sufficient free disk space, also helps prevent slowdowns.

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