Hello there, @RKT1.
Currently, switching from QuickBooks Online (QBO) to QuickBooks Self-Employed (QBSE) is unavailable.
While QBO gives you the option to upgrade your service, you can't migrate directly to QBSE. This is because they're totally different programs and are designed for different types of businesses.
In the meantime, if you want to open the two accounts at the same time. You'll need to use a different link to open it.
For future reference about QuickBooks Online and Self Employed, here's an article for more information.
We're here to help if you have any other concerns.
