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
a) install older FW (e.g. 126.96.36.199)
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