Welcome to the forum - A search will find you several threads discussing this. There is a known bug with connecting to a small number of specific routers that is being worked on which is the primary cause of the issue, and hopefully there will be an update to resolves it for iodéOS (its a combined OS & hardware issue).
In the meantime you will need to look through these and check if you have the same situation, or the same router, or similar, that others who have had the issue (in which case it may not be fixable right now) - and/or try some of the suggested actions to see if it resolves it:
The official one:
Also these - unfortunately many duplicate info, but hopefully you will find things to check or try and/or identify if your router is one of the ones that the phone and it won’t play nicely together…
I have an odd situation. My Brax3 was working perfectly fine on my private home wifi until this past weekend, when it disconnected on its own and now it will not reconnect, saying the typical (saved/check password and try again.) What am I supposed to do about that? My Bell internet/wireless router is a Segamcom Fast 5566, Home Hub 3000.