crystal reports 13 Oracle connection problem

I'm trying to migrate a small .NET application (VS2008, Crystal Report 10, OS Win7 32-bit) The application has got 2 reports that use some data of an oracle database version 11g Release 2 (11.2.0.1).

When I upgrade the application (VS2019Pro, latest Crystal Report (CR13SP25), OS Win10 64-bit) the application itself runs as expected and the 2 crystal reports show the proper data. It's only when I open Database Expert in crystal report designer and try to access the Oracle connection, I receive an error when trying to pull the list of tables of that connection. I've tried all 3 possible Oracle connections and all of them give a (different) error: (1) Microsoft OLE DB Provider for Oracle (MSDAORA): "ADO error code: 0x80004005 - Error while trying to retrieve text for error ORA-01019" (2) OLE DB for Oracle (OraOLEDB.Oracle): "ADO error code: 0x8000ffff" (3) Oracle Server (crdb oracle): "Unknown error in database connector"

Now the weird part is that sometimes I do have access to those 3 connections in Database Expert, meaning the list of tables becomes visible. This happens very rarely and doesn't last for a long time. I've also noticed that when this happens I can access all 3 different connections, so it's "all or nothing".

This behaviour is the same when I create a new solution and add a new crystal report or when I use Visual Studio 2017 Professional instead of 2019.

Anybody has an idea on how to fix this kind of behaviour? Thanks in advance!

Finally managed to solve this one. First I opened the old project in Visual Studio 2019, triggering the conversion screens of both the solution itself and Crystal Reports (choose Yes). Since my original solution was using the (obsolete) Microsoft OLE DB connection for Oracle I’d first created a new connection, in Database Expert (in An existing Crystal Report), that used the OLE DB provider of Oracle situated in OLE DB (ADO). Next I replaced the old connection by the new one (again in Database Expert). After applying this to all of the existing reports, everything was working properly!