iPhone 13 Pro Max internet WIFI connectivity

Even before the ios 16 update my handset was playing-up in regards to connecting to WIFI.

IE. It doesn't connect - In truth it appears to connect for about ¼ a second! (sometimes).

Home wifi is functioning fine on all other devices. Home network has been reset and turned on - pause for 20 secs and restarted - no change.

I have turned handset wifi-toggle on and off = no change

Reset network on phone = no change

Forgotten Home network - rejoined = no change

Turned phone off off - walked away for 30 mins and come back/turned on = no change

I have checked phone for damage or an incident where it might of been damaged = None and no history to indicate misuse - Only owned phone for about a month!

Any help or ideas please.......

Grateful