i think this is a very common and old issue with OSCLASS. When a user publishes an item and the admin has to approve it, it will not show up in the items list until the admin approves it but disappears and sometimes the user repeats it in doubt. There should be a status of pending listing e.g. "Awaiting approval". In my case, I am using the Tatiana theme but this issue is not related to this theme only it is a general issue if I am not wrong. The team need to help please.

Validation feature is usually granted by some plugin. In that case is not that simple do such section.