Restart your device and turn off and turn it on back after some time

To use volte then sms ACTVOLTE to 12345 and wait for 2 hours your volte will be enabled

If you use vi sim for vowifi feature is disappeared to use vi vowifi send ACTVOLTE to 12345 and insert Airtel or jio sim in 2nd sim slot then you will get option to use vowifi for sim 1 and sim 2 then it will work

Try reseting your network settings or reinstall youtube