I paid the Quickbooks subscription as I was on a trial but the subscription is not showing up in Quickbooks---. The subscription is not linking to my account

How did you pay it? If you are using the trial account, you have to go to the the Billing and Subscription menu to pay the regular rate. If you were clicking the Buy button, it would open a new blank QBO account.

https://quickbooks.grsm.io/EU