With regards to remote not connecting on the TV that is currently not working on, can you swap back to the other television and then on your Router try a different wifi channel.
if your Router is dual band then try both the 2.4ghz & 5ghz networks on the Stick, then swap back to the other television that the Stick is not working on, where it sounds like a wifi problem to me when using the television that doesn't currently work on the Stick and can't communicate over wifi.
The On / Off standby and volume buttons, doesn't work on all brand televisions.
If you can get the Stick working again on your television that doesn't currently work with the Stick, then have you tried going into the Stick menu settings under control remote for television and gone through each code a step at a time during the setup wizard.
Out of curiosity what is the make of the television, where certain low end or supermarket televisions there may be a different brand name you can try, where certain brands are out sourced by another manufacturer with a different badge on it.