With Simatic Option+ Manager running on a PC I move files from 4 HMI (TP Comfort)  to 4 PC folder's; now i try to do the same witha fifth HMI but Simatic Option+ Manager give me the error "could not login".

webserver username and password (administartor) are the same configurated in Simatic Optio+Manager, other settings are the same of the others hmi

Where could be the issue?