I assume no-one has tried the simplest thing first? It may not be the problem but for a few seconds effort its probably worth a try.Often routers can get a little confused over time, and all kinds of wierd and wonderful behaviour can result. Have you tried power cycling the router? This sounds fancy but all it actually means is to switch the thing off for a minute or two. Pull the power cord from the back of the router, wait about 60 seconds, then plug it back in.If you know the router settings and how to access them, then resetting the router and re-entering the correct settings can often make a difference too as the next step.
Mitz from Tips4pc