Since version 15.2.0 on my MacOS - it broke my system. A blank Premiere project shows no Audio tracks, no Video tracks, no Clip Mix channels - nothing. I have to create a blank Black Video and drag it to the Timeline to get it to do anything. This seems really problematic.
Sorry to hear about your frustration. It sounds like you just need to reopen the sequence and/or get Source Patching set up properly. Can you show us a screenshot of your Project panel and Timeline? Then we can assist you with less confusion. Hope to help.