My WiFi connection doesn't recognize my router password
My Imac doesn't seem to recognize my wifi password
Question marked as
If you are able to log in with the same password using other devices then try restarting your iMac and then try again. On rare occasions when I have had a similar issue that has worked for me.
If restarting doesn't work then try creating a new user to see if the issue is tied to a specific user.
How to test an issue in another user account on your Mac - Apple Support
If you are eventually able to connect to WiFi but continue having issues then this article may help:
If your Mac doesn't connect to the Internet over Wi-Fi - Apple Support