Application Error after upgrading Heroku

[acba...@gmail.com]

Hello,

I had not used my oTree app on Heroku for a while and when I recently tried to push new code to Heroku I got an error message that said I needed to upgrade to Heroku-20. When I did and redeployed my app, I get the following error page:

"An error occurred in the application and your page could not be served. If you are the application owner, check your logs for details. You can do this from the Heroku CLI with the command
heroku logs --tail"

When I check my logs on Heroku, I get the following:

Does anyone have any suggestions how to fix this? I honestly don't even know where to start.

Thank you!