Chromecast Problem

[ladyalex]

Can anyone help with a Chromecast problem ?
We had one which worked perfectly for some time, then we stopped using it for several months . When we tried it again, it just wouldn't connect. So we got a new, slightly different one. (Circular rather than sort of pear shaped like the old one.)
Unfortunately we cannot get it to work. It occasionally starts to cast, but after we shut it down, it will not connect again. This is usually fixed by restarting the tablet/phone but this is really not satisfactory. We have HomeHub 6 from BT and our internet is usually reasonably reliable.
I cannot tell you how many hours I have spent recently staring at Google Home whilst it tells me 'no devices detected' when I know that there is one plugged into the TV barely 4 feet away.
Thanks for any suggestions.....but please don't say restart things...we've restarted everything many many times .
:-))