A RedirectURI usually should end in a /
I predict the issue is that the panel/console has auto added a / to the end (usually chrome auto fill)
Hence the conflict.
Check that you are using the correct clientID in your code as well
At the moment I cannot replicate your issue, but I end all my redirect URI’s with /
Additionally if you have changed your redirect URI, it’ll take 2/3 minutes before the changes are replicated “on production”