It is hard to guess the reason of the problem without any details, but let me describe here some most frequent mistakes which users do when deploying to Jelastic.
If you use PostgreSQL in Cloud you should generate all the scripts before building WAR. It means you should adjust connection to some PostgreSQL DBMS, generate and save DB scripts. It is also good to start the application with PostgreSQL locally and ensure that it works well.
When you add a PostgreSQL-node to your environment (or Studio creates it), Jelastic sends you an email with credentials. Using that credentials you should log in the Postgres PHP admin (the link is in the email) and create a new DB. After that, as written in the documentation, you can generate custom context.xml in Studio and specify there the created database, host and credentials from the email.
Studio only adds a node to created environment: automatic database creation in Cloud is impossible, so you ought to do it by yourself.
- If your CUBA application is heavy (has lots of entities and screens, uses premium components) 6 cloudlets assigned for Tomcat by default could be not enough. So try to increase it using Jelastic administrative panel.
What I should also mention here: Jelastic user can see Tomcat logs using Jelastic administrative panel. You can investigate almost all the problems by viewing the Catalina.out log.