Hello,
If its didn't allow to change the password from the browser. Try to login on different browser and try to reset the password. If that also didn't work then try to do the Factory reset physically from camera device. ( Read operations manual for instructions.)
Then try to access the cameras and try to set the password. Hope that work fine then, if not then open TAC case with us, will check once and proceed for replacements for this parts.
Thanks,
Jayesh