You need to log in to the terminal via ssh or perhaps the digital ocean console.
Then you can
./launcher rebuild app
It’s a good bet that it’s been so long since you’ve done that, that you’ll need to upgrade postgres (PostgreSQL 15 update. But it’s also a pretty good bet that you can just do that rebuild again and it’ll all be done.
You might first need to upgrade docker.
It’s also possible that your os is beyond end of life, which can make upgrading docker harder. (but maybe “apt update; apt upgrade” will do it.)
If you’d rather not learn that you can ask for help in Marketplace and someone like me can make it work for you.