I bought a used Linksys WRT1900ACS router on eBay. I got it for $50. New it goes for close to $200. IT works. But none of the lights on the router go on! At first, I thought it is defective, and the seller agreed to take it back. But then I tried using it, and it works. When I turn it on, the LED's on the router flash for a fraction of second and then stop and never light up again. Does this mean this router is going bad? Or could it work well and worth the risk of keeping it?
Port lights will be ON when an active device is connected to that port, lights OFF if nothing connected. So try connecting a device and see. Also the power light should be ON. It may flash until the router is ready and then be stable ON.
If after the above, lights do not stay on, then ask to return it.
There's a bit of discussion on the 'net about this model, and possibly other similar models. The discussion I read mostly suggests that Linksys attempted to use small LEDs for the panel that were incapable of handling the intensity desired by the engineers. As a result, they ceased to operate.
With your start-up flash, that may not be the circumstance described in the linked forum. Running from that point, I discovered reference to some firmware versions allowed one to reduce the intensity and/or disable the LEDs completely using a smart-phone application. I was unable to pin that information down, but also found references that indicate newer firmware removed that feature.
If you've not performed a factory reset, try that, as it may return the functionality of the LEDs. I suspect you have performed a reset, as that's the most logical step when receiving a piece of equipment from the outside world.