RT-N66R stopped working, lights flashing

[Slickone]

This router is only used to plug a VoIP phone into, which connects wirelessly (set to media bridge) to an RT-AC86U.

When the router was turned on today (it's turned off nightly), the VoIP phone had no signal, and the router gives a series of blinking lights:
All the lights flash on for a second, then turn off with only the power and two lights on the right still on. FYI, the two on the right at USB and 5Ghz, neither of which are used. A few seconds later, it does this routine a second and I think a third time, and then those two right lights flicker, then stay on *while* the power light flashes off and on.

Is this a code that means something other than being bad?

Also, if it's bad, is there any reason I can't use another brand to do the same thing? I have an old Linksys WRT54G. I may even have a Linksys AC1200 router.

 

[Tech9]

I may even have a Linksys AC1200 router.

Linksys E5400 works well as wireless client. It has a Bridge Mode in firmware. I have 2x in use on my home network.

Very small and cheap device, was like $30 from BestBuy. One is serving exactly my VoIP ATA. No issues, set and forget.

The price is still the same, Amazon:

 

[ScubaCat]

Also, if it's bad, is there any reason I can't use another brand to do the same thing? I have an old Linksys WRT54G. I may even have a Linksys AC1200 router.

I use an old WRT54G as a bridge. I flashed DD-WRT firmware on it about 10 years ago.. watched youtube and netflix with a device plugged into it as recently last night. It seems to be *much* faster than connecting wifi directly from each device, especially the game consoles.