I exclusively use adobe Media Encoder to export from premiere so when media encoder auto-updated, I was forced to update premiere to the 2021 version. I opened a project that I was in the middle of in 2021 premiere and it saved as a new version which it does every time I update. So, I didn't expect to have a problem and it shocked me when my audio wasn't playing. I narrowed down the problem to the "fill right with left" effect I had on my audio. Somehow, the 2021 version of Premiere swapped the "fill right with left" effect to "fill left with right" effect, making my audio disappear. and deleting the effect and reapplying it fixes the issue. Hopefully someone can find this useful!
Audio, Editing, Effects and Titles, Error or problem