Login problem

Hi there, 
Sometime ago i bought a device, and created account under my email, and everything worked.
But I could never be able to open my personal account to see my bills and everything else. 
 

• I can login with my email and password.
• It logs me in
• I see my user name on the O2

When i want to open my personal account, it always re-directs to the https://hilfe.o2online.de/ (on web) 

and on Mobile app, it always closes with a error. 

How can I resolve this issue? It is something normal and specific for my case? 

Thanks for your help