The problem is related to NTP settings and especially the way the clock which drives the Wireguard drifts (since routers don’t have a RTC built-in).After a while, or when you have turned off the router for a day or two and try to reconnect, it becomes a problem..
For your internet to work, Wireguard must work (since you’re tunneling WAN traffic through it).
For Wireguard to work, it depends on a monolithic timestamp (meaning it must always go forward). If router has been powered off for a while, the date will be all sorts of wrong. And so, the NTP settings must correct this on startup.
For NTP settings to work, you need internet to work (back on square 1).
Some people have suggestion to manually set the time (2030-10-10 – 10.00 for example) during initial startup everytime you reboot. To trick WG, and then it will be set correctly when NTP syncs. And a cron job every hour or so to correct the drift. This has worked a while for me, but it always screws up sooner or later. Hopefully this can be better optimised or fixed.
If it would be possible to route NTP through ISP internet (not VPN) and have it sync once in a while (like a watchdog timer). It would fix WireGuard.
