Suddenly, newly installed or updated apps won't launch

Running Big Sur, v11.7.4, fully up to date, on a MacBook Air, Early 2014, as a Standard user (with known Admin credentials). I did recently install an update to Big Sur maybe a few days ago, but as I haven't recently installed any new apps, I can't be sure when this problem started or if it has anything to do with the update. # The Problem Begins I was trying to transfer some files to an Android phone so I launched the app *Android File Transfer* which was already installed on my computer. The app launched immediately but it wasn't seeing my phone. I hadn't used *Android File Transfer* in over a year, or more, so I thought I'd rule out an app issue by downloading the latest version of and updating the current version. That took me all of two minutes. I overwrote the current version with the new download and tried to launch it... and it just started bouncing in the dock... forever. What's even weirder is that after double-checking, I realized that the "new" version I installed was the same as the already-installed version. I guess *Android File Transfer* hasn't updated in a while. But why was it starting fine before and now it won't start if it is the *exact same app and version*? I tried Force Closing and relaunching, I tried restarting the computer and relaunching, and I tried logging in directly as the Admin user, I tried completely uninstalling (Move to Trash) and then reinstalling the app: the app just won't start. I figured out another way to get done what I needed with my Android phone, so I left that aside since everything else was working fine, and I don't really use *Android File Transfer* much. # The Problem Continues Then today, I needed to consolidate two similar folders. I pulled up the already-installed app *Beyond Compare*. It opened immediately without any problems. The app launched immediately without any problems, but this is also an app that I again hadn't used in a while, so again I decided to check for updates before continuing. It turns out I was on v4.3.7 build 25118 and v4.4.6 build 27371 was available on the website. I downloaded it from the website, extracted it, and then overwrote the existing install in the Applications folder... ...and now the app won't start. It's the exact same symptoms as above. It bounces forever in the Dock and never stops. I tried overwriting it again, I tried logging in as the admin user, I tried uninstalling (Move to Trash) and then reinstalling the app, and I even tried rolling back to the original version which started up just fine (v4.3.7). Nothing works: the app never starts, *not even the older version which had just launched with no problems minutes before*. # Help What the hell is going on and how can I go about troubleshooting/fixing this? I would try with updating another app, but now I'm a bit hesitant. So far both these apps are apps I rarely use. I don’t want to compromise an application I use daily. # Update **Edit 1:** So I experimented with another program I have installed: *IINA*. As I also have *VideoLAN* installed, I can get by if something goes wrong with *IINA* (which is also another great video player). I currently have *IINA* v1.3.1 installed, and it launches and works wonderfully. As the [*IINA* website states](https://iina.io/) , it requires macOS version 10.11 or higher to run, so there shouldn't be any problem with it running on Big Sur (11.7). I re-downloaded the DMG file for *IINA* v1.3.1 from their website and copied the app into my Applications directory, overwriting the current install. As predicted, I am getting the exact same behavior now. The app icon appears in the Dock, starts bouncing forever, and never successfully launches (whereas before it would launch quickly and without issue). Something is going wrong with my macOS when it writes new apps to the Applications directory. How do I figure out this problem? **Edit 2:** The problem is definitely related to the specific user profile. I created a brand new test profile, and I was able to launch all of the problematic programs with no problems. Something is happening on my main Standard user profile *only* when programs are installed (copied to the Applications folder) or updated (copied to and overwriting the existing app in the Applications folder). But that same new program or overwritten program will work just fine in the new user profile. What gives? What is unique to the user profile related to apps that could be causing this?