Is this happening on all devices? Which ones are you using and what version OS are they using?
Have you cleared out the wifi from all previous wifi connections? This is important.
Just for example on my current computer where I have done a lot of configuration of different routers I have 30 registered wifi connections. I cannot show them all but there are multiple full screens of them.
To get things working correctly I need to delete the whole lot.. just select all of them.. and delete the whole lot.
And use the - in the box below it.
Once you have empty box.. I recommend you reboot the device..
Then reconnect to the wifi.. so you have just a single wifi connection available.
Does that help??
Would like to just change the password at last resort, but don't know how.
Change password is easy..
But it will depend on what router you have.. it is done on the router .. so read the manual on how to change wifi password. As BTW it is often easier to change wifi name along with the password.
Since this forum area is airport routers and hopefully that is the router you have.. to change wifi password.. go to the airport utility and click the icon of your airport.
Then click the edit button bottom right of the summary popup and go to the wireless tab.
Type in a new password and click Update ..
Basically same on any router you own.
My Synology main router.. go to the wireless configuration..
Type in a new password.. and click apply.. done.