Access to resource forbidden (Sharepoint folder)

It happened suddenly. No the reason why. I lost the ability to refresh amy data fromSharepoint folder.

Got the following error:

I havent changed any credentials. So far it was automaticly connecting. Suddenly stopped working.

Suspicious is, this happened exactly one month after I first time installed Power BI desktop in the current organizaion. 

Non of the login options (as on the first screen) does not work. I can normally use Sharepoint folder but lost access via Power Bi.

I am using latest PB Desktop release