Thanks for reaching out the Community, aden1.
Switching back to Automated Sales Tax is irreversible, especially if you've migrated to this new feature from the old sale tax.
Since you're unable to switch back to the new feature, I highly recommend contacting our QuickBooks Support Team. They have the tools to help enable this in your account.
To reach them:
I'm linking an article just in case you need a reference on how the automated sales tax feature works.
That's it. Please let me know how it goes. I'll be here to keep helping. Have a great day.