I'm here to ensure that you'll be able to retrieve your data. To start with, the 50% discount offered for QuickBooks Self-Employed subscription is only applicable to new users.
In your case, there's a possibility that you've created another account upon availing the said discount. To get this sorted out, I recommend and accessing your company file using the old and proper credentials. This way you'll be able to have your data back.
On the other hand, if you want to keep the current subscription that you've purchased (through the 50% discount), you can export and import your old data there.
Otherwise, if you'd like to utilize your previous account, you may cancel the one that you've currently subscribed to.
You may have more than one QBSE account with the same email address. If you have to open a new QBO account, make sure to click the Buy button to get the discounted price for up to 6 months. If you purchase from the trial account, you have to pay the regular price. We have yet to find any 3rd party migration tool for QBSE.