What happens when you try?
Did you try a
./launcher start app
But you probably need to
./launcher rebuild app
But, as I stated earlier, you have likely rebuilt enough times that you are hitting let’s encrypt’s rate limits. You can either wait a week or try Setting up Let’s Encrypt with Multiple Domains and just add some other subdomain (that you first create a DNS entry pointing to your server) and try rebuilding again.
You can look at
tail /var/discourse/shared/standalone/logs/var-log/nginx/error.log
to see nginx errors.