Unfortunately, our app in version 1.5.4 is not able to create the user in the FW 6.50.4 on older cameras.
1st solution: use the newest version of application 3.X
2nd solution:
a) install older FW (e.g. 6.50.3.1)
b) default your camera (Restore which keeps IP settings is sufficient)
c) install CamStreamer App 1.5.4 again
Impacted cameras: Q6128-E, P1428-E