Different ways to fix YouTube premium not working issue
Check the subscription status
It could be that your subscription may be out of date as a result of which you may be facing the issue. All you need to do is renew the subscription and then access YouTube premium account. Things should now be working for you without any hassles.
Check the Connectivity
It may be that you may not be connected to the internet at all as a result of which you may be facing the issue.
All you need to do is check the connectivity and then things should certainly be working for you.
Payment Failure
It may be that you may have tried to make the payment but the payment may have failed as a result of which the subscription may not have been activated.
If there is a payment failure then you should re-do the payment and then access the services of YouTube premium.