Have you tired turning it off and on again?
I'm in the midst of finally turning my attic space from a spare room with office set-up to a proper workspace with sleeping facilities. Over the decade since I moved in, success unclutterings of downstairs and the bedroom have left the attic laden with lots of boxes, a sagging bit of ceiling panel and the shelves I found in a skip 15 years ago. Next weekend is a long one, so I'm planning to refit the difficult end of the room (the bit with the sagging panel), but I'll still need my PC. So this morning has been spent shoving sofas around downstairs and setting up the PC in the corner on the new desk.
All went well till the final stage. I successfully moved sofas without finding extra kills under them. I got the PC downstairs and didn't drop the heavy monitor. I disconnected the wifi bits as the temporary workspace is about 2m from the network router box and I've a CAT5 that will reach. I connected everything up...and got 'local connection only' on the network connection. A call to a 25p/min helpline produced the following answer: switch the router off and back on again. And it works!
The IT crowd were right.