No access to webstats after upgrade to Onyx

Hi all

In December I upgraded from 12.5 to Onyx without any problems.
With 1 exception: since upgrade I do not have access anymore to the webstats.
Tried both, admin and customer account, without success

My site is on SSL, nevertheless I tried both, domain.com/plesk-stat/webstat-ssl/ and domain.com/plesk-stat/webstat/. Both with same result as described above.

Any help would be appreciated.