@Archer_VR-900. 

I hope you have got this issue resolved already.

But if not, please help check some details, then we can try to figure it out:

1. When this issue happens, all the devices fail to access the internet, including the wired and wireless? Are you able to ping the VR900, how about ping www.google.com?
2. Please check and confirm is the internet light on the VR900 still correctly on or flashing when the internet stops.
3. It is suggested to reset the modem to factory defaults, then reconfigure it from scratch to confirm.
4. BTW, how often does this issue happen? Are there any special operation or activity in the network may cause this?