Sky fibre shows connected but can’t connect phones or games consoles

[Spud69]

This is driving me mad. Upgraded to sky fibre and since then have had issue after issue 

Firstly - sky Q main box wouldn't update and froze so was replaced. The new box would connect then drop the connection two or three times a minute. This affected the picture stuttering on this box and the two mini boxes we have. 
Secondly- Have to reset the box every single day. We are using the black router we had with sky fibre as this  wasn't upgraded when we upgraded to FTTP 

Thirdly - and the real issue is our network and box shows connected, however our phones do not connect neither do our sons games console. These were connected up until a week ago. This means we can't work from home. 
An engineer is booked for next week but after spending nearly three hours on the phone setting and resetting everything and getting nowhere I'm hoping the engineer will find the reason. 

Any ideas? I've tried absolutely everything 

[Chrisee]

@Spud69 if an engineer is booked it is pretty pointless forum members recommending things as most suggestions will have been covered during the call you had with Sky.

However some background may help if the black router is the upright SR203 Sky Broadband Hub you have the correct router. If the hub is in the same physical location as when it was connected to the old copper connection its wifi performance should not have changed. It is a wifi5 unit and provides speeds up to around 650Mb/s.

If however the ONT's location has changed the wifi performance maybe compromised if the hub is on the floor or in a cupboard etc. Any wifi source should be in the open and ideally above things like radiators that can  block the signal.