Wifi disappears when I try to connect Chromebook

[#1]

I'm having a problem with my wifi disappearing when I turn on my Chromebook (Pixelbook Go).  I've had the device a year and had no problems until I connected it to the router via ethernet cable a few days ago (I was planning to change my wifi password).  When I plugged in the cable the wifi went down on my other devices.  I disconnected the cable and the wifi came back but for a while I had trouble connecting the Chromebook to wifi again (I hadn't changed the wifi password so it was nothing to do with that).  After a few minutes it connected and seemed ok.  But when I turned it on again this morning the wifi disappeared again (no connection for any of my devices).  If I close the Chromebook down or turn off the wifi the wifi comes on again for the rest of my devices.  I connected the Chromebook by ethernet again and it worked and this time the wifi stayed on for my other devices.  But once I disconnected the ethernet whenever I turn on the Chromebook the wifi drops off (and the lights go out on the router).  My router is an old Thomson Gateway TG585v8.  Generally it works ok though the connection to my desktop tends to drop off when it is in sleep mode but reconnects when I start using it again.  Has anyone got any idea why this has happened and what I can do about it?

[#2]

The TG585 v8 must be more than 8 years old?   It predates current model Sagemcom 2704n Hub Zero and previous TG582n.

I would suggest you simply replace it with a newer model to see if it resolves the issue. 

I would suggest you contact Plusnet direct.  If you recently renewed your contract, they will usually send you a hub for free.

Otherwise, look on eBay for a new or used Plusnet hub for around 10 quid. ie. Sagemcom 2704n Hub Zero, or even a Hub One (there are known wifi issues)

You may wish to consider the far superior BT smart hub (type 1A) too.

[#3]

@bill888 

Whatever you do don't buy a hub from Plusnet. The freebie 2704N is arguably worth the P&P charge but in my opinion even that is debateable.

As @bill888 says, the BT Smarthub 6 is far better than either of Plusnet's offerings and is available from an auction site for about £20 or less. Setting instructions are here:  https://community.plus.net/t5/My-Router/Using-the-BT-Smarthub-6-on-a-Plusnet-Account/m-p/1587673#M85...