Applications not opening after replacing MagSafe DC-In and battery

After following and completing these guides: MagSafe DC-In Board, and Battery Replacement, and allowing the battery to charge (which it did), I started up the laptop. Everything seemed to be working normally for a few minutes, until I noticed issues trying to open and run just about anything. Finder works, but anytime I try opening a file, it says "You can't open the application ______ because it may be damaged or incomplete."

Strange thing was that I was able to use a couple apps for a few minutes, but after some time had passed, they would not open again. Even apps such as Activity Monitor and System Preferences respond the same way. I fear I may have damaged something while removing and putting back the logic board.

Any advice is welcome.

This fixed the problem (so far!):

https://techwiser.com/fixed-macos-error-...