I've been using the same custom launcher for over 4 years and recently I had a lot of problems installing forge into it. After 1.12 it didn't see any forge versions but I still got it to work. However it does not see any 1.14+ forge versions. I don't want to use the official launcher it doesn't see any of my other forge installs(1.7.10, 1.8, etc), only the 1.12+ ones. The launcher is called TLauncher 1.110.4 Legacy.