Startup Issue with Minecraft - Instance will not start up

[ThePotatoKing]

Maybe try updating your instances tomorrow after the next mainline update is released tomorrow.
In the meantime you could try going through this post to see if it’s just some weird windows issue:

Something not working on Windows? Try the following:

Windows has a habit of making life difficult for AMP by ignoring its requests to not cache certain AMP components, meaning that things can often get a little rocky after an update. If this happens to you - go through the following steps: Follow these steps in the exact order given, do not skip any steps, Stop AMP fully by running ampinstmgr stopall in a new command prompt. Use Task Manager to make sure all AMP.exe and AMPService.exe processes are stopped. Download a fresh copy of AMPSetup.m…