Broadband very flakely on all devices for last 2 days

[JAKid]

Broadband very hit and miss.  

Service checker says good but sky auto phone service says a problem.  Sent me a text with checkers etc but done all that and did it again.  Still have problem

All devices are saying good

Can not even get into sky router ip address. 

Have rebooted router, laptop, phones etc several times in last 2 days.  

A windows diagnostic troubleshooter said ' wifi doesn't have valid ip configuration. 

Wifi has happily worked before all this!! I use it a lot for my work.  

[JAKid]

Added information

2 days ago started dropping off. No new devices added.

Turned off router, unplugged everything.  Did that about 5 times.   Even left off for an hour once instead of 10 min

Affecting all devices (laptop, camera, phones etc)

Yesterday was fine for 5 hrs and then did the same, flaky.  

• This morning flaky.   currently saying have Internet but can't get into several sites including sky router !