I can't update my MacBook Pro to macOS Catalina

Yes— this is a common problem...

Catalina not available for download

running Mojave 10.14.6.—trying to download Catalina, it is not showing up as a system update

From the Applications/Utilities/Terminal.app copy and paste:

sudo softwareupdate --reset-ignored

(please note your psswd will not echo on screen—type it in anyway to proceed)

relaunch System Preferences>Software update

Look at System Preferences> Software Update to see if it is there:

You may have to take care of the "Another update is available" part (red box) before Catalina shows as in the above example.