When developing in .Net Core 2.2 sometimes when there is a configuration error, the debugger fails to attach to the Server process.
Check in the appsettings.json of anything that you added, normally if there is an error, you will see a squiggly line on it. - Best practice, code in chunks and see if it breaks anything. I mean to write one line of code and check if it passes or no errors happen. Normally this is how development is done when you are learning a new technology on the block.
This might be due to the mix of libraries from other versions of .Net Core e.g. If you attempted to upgrade ASP.Net Core 2.2 to version 3.1 all library dependencies are supposed to be upgraded as well.
Make sure that you do not have any duplicates of dependencies in the Dependency Injection Container in startup.cs.