Also on my MI 10 Lite 5G in phone information both the VOLTE and WiFi calling provisioned switches show as off, But both are enabled in the SIM settings and work.
When you put the codes in the message that pops up should say disabled, If it said enabled you need to do it again. After you need to restart your phone. Then go into the SIM card settings and check Volte / WiFi calling are enabled. If it still does not work make sure the SIM card is in slot 1.