Problem with opening reports on iOS and Android (report server on-prem).

Hi guys, 

I have a problem with our reporting server (on prem). 

I can connect to it and see all the files and structure on iOS and Android but I cant open any reports. 

The "wheel" keeps on spinning and then all I see is a white page. 

Reporting Server:  1.4.6969.7395 (January 2019)

SQL: 2017 CU13 

App version: Latest on both iOS and Android 

Best regards,

Martin