Getting "There was a server error processing your request" for new app authorization

I’m trying to authorize a new app by redirecting user to[client_id]&redirect_uri=[redirectUrl]&scope=full&response_type=code
This brings up a login screen, but then instead of giving an option to authorize the app, there is an error
“There was a server error processing your request”.
What am I missing?
Have two other apps integrated earlier, and the authorization workflow worked for them.

That’s an incorrect address, you’ll want to use[client_id]&redirect_uri=[recirectUrl&response_type=code&scope=full