We we have to keep resetting out broadband modem and router. The service drops out and asks for our password which we enter correctly but we get an error message saying invalid password. We then reset both the modem and router and it then accepts our password. This happens around 15 times per week. Very frustrating.
Plus the range on he WiFi seems to have diminished and now doesn’t cover the whole house any more.
when you say 'service.. asks for our password', is it your phone/PC asking for the wifi password?
by 'reset' do you mean factory reset or just a reboot (power cycle)?
That said, I'll take a guess based on what you've given. Possible the 5G and 2.4G SSIDs (wifi names) have different passwords configured on the router, and your phone/PC has them configured the same (or vice versa). Log into the router and configure different SSID names (eg Mike-2 & Mike-5) but with the same password, then on your phone/PC delete/forget the network settings for both SSIDs and reconnect with the new password.
The range issues you've got may be related here - 2.4G gives greater range but suffers from interference and can drop out if close to a neighbour's wifi signal. 5G is faster and less susceptible to interference, but shorter range. Get the SSIDs working as above, then test & choose the best.