mistakenly canceled my yearly subscription

Hi @sysadmin - Are you certain that you no longer have access to paid features? When you cancel a subscription online, the cancellation is effective at the end of the subscription period that you paid for. You've essentially disabled auto-renewal by cancelling. 

If you no longer have access to your paid features, I recommend that you submit a request to Zoom Billing for assistance. They will need to access your account to investigate further.