All,
Thanks for your input. Finally, we were able to resolve the issue on both environments, although I am not completely clear on what actually helped. For each environment, the steps that finally led to a solution, were different.
Let me sum up the steps, as I hope this might help someone with a similar issue.
DEV: As their databases are placed on a RAC, on exadata, the DBA suggested to temporarily shut down an instance in each DB cluster and keep only one instance running for each of the 3 databases (Clarity DB, Data Warehouse and Jasper DB). This alone allowed me to run the "admin update jasperParameters" command and the system was back up. After that, we reactivated the full RAC and everything works fine.
TEST: The above steps did not help on TEST. Therefore, we kept trying and searching for a solution. In CSA, in the tab Database and Data Warehouse, we unchecked the box Specify URL and tried to define the connection in another way. In the end, that was not possible, so we switched the box Specify URL on again and put back the original settings. Just the fact of changing the connection details and changing them back again probably moved something and after that, everything started working.
As I say, I am not sure what exactly is behind this solution, but if you are in the same situation, you might want to try that too.
If anyone has any insight on what I wrote above, I would be interested.
Thanks