Unable to download upgrade to macOS mojave 10.14.6 from high sierra

Mac friends... I need your assistance!

I get an error message that reads: "This copy of the install macOS Mojave application is damaged, and can't be used to install macOS..."

My ultimate goal is purchase Final Cut Pro, but I  get a message that reads: "Final Cut Pro X can’t be installed on “Macintosh HD” because macOS version 10.14.6 or later is required."

Should I just skip over Mojave and go straight to Catalina? I know there's some issues with the Mojave 32 bit verses the Catalina 64 bit... I really don't want to skip an upgrade if there's a better option out there.

Any advice would be most appreciated.....

Thank you in advance!!

James