moving an Apex app from a server with Apex 4.2 to another server with Apex 20.1: all access to proce

I export an Apex app from a server with Oracle 11.2.0.4/Apex 4.2/ORDS 2.0,  and then import it to another (new) server with Oracle Express 18c/Apex 20.1/ORDS 19.2. The pages are displayed, but whenever a process needs to be executed, the page stops with the error "Insufficient Privileges".

Re-creating those processes seems fixing some of them, but not all of them. Even if re-creating fixes the problem, I cannot re-create all of them.

Creating a new application with a few processes works just fine.

I would appreciate any advice

Thanks,

Vu