First, run First Aid:
Repair the Drive for El Capitan or Later
- Restart the computer. Immediately, at or before the chime, hold down the Command and R keys until the Apple logo and progress bar appear. Wait until the Utility Menu appears.
- Select Disk Utility and press the Continue button.
- Then select the indented (usually, Macintosh HD) volume entry from the side list.
- Click on the First Aid button in the toolbar and wait for the Done button to activate. Click on it, then quit Disk Utility.
- Select Restart from the Apple menu.
Now, Download and Install the macOS Catalina 10.15.3 Combo Update. See if this fixes the problem. If it doesn't, then do the following:
Reinstall El Capitan or Later Without Erasing Drive
Please be sure you back up, if possible.
- Restart the computer. Immediately, at or before the chime, hold down the Command and R keys until the Apple logo and progress bar appear. Wait until the Utility Menu appears.
- Select Disk Utility and click on the Continue button.
- Select the indented (usually, Macintosh HD) volume entry from the side list.
- Click on the First Aid button in Disk Utility's toolbar. Wait until the Done button activates, then click on it.
- Quit Disk Utility and return to the Utility Menu.
- Select Install OS X and click on the Continue button.