Hi Abar,
Your Mendix application is currently unable to connect because the PostgreSQL server is still in the process of starting up and isn't ready to accept connections yet.
This is a database-side issue, not a problem with the application itself.
It's a temporary startup delay with PostgreSQL—not a bug in Mendix or your app.
Please wait a few minutes, then check the database status in RDS (or your hosting platform). Once the database is fully operational, you can restart the application.
Database size is full. Thats the reason application went down. Increase the container size to bring the application up.