When the first time you get the VIXMINI router, you must setup an admin password. If you forget it, you need to reset the router to set a new admin password. When you press and hold the reset button for more than 10 seconds to reset it, the light will flash like crazy for a while and then it will go out. When it’s back again, it’s reset successfully. Then, you can do the first-time setup all over again by visiting the admin panel on 192.168.8.1.
It’s fine if you don’t want to reset your cameras, I guess your cameras were connect to another wifi before and they are still looking for the old wifi SSID and password.
I am not very sure about the role of your D-Link router in your user case. Do you want to use the D-link router as main router and VIXMINI as a wireless repeater?
When you said the the two routers sharing the same “username” and “password”, do you mean the wifi name and wifi password?