I'd be happy to help you convert your QuickBooks Online back to QuickBooks for Mac.
To convert from QuickBooks Online to Mac, you need to export the file to QuickBooks Desktop Windows then convert the Windows file to Mac. You can subscribe to a free trial version of QuickBooks Desktop Windows so you can complete the conversion.
Here are the links that provides the step by step process for your reference:
However, if you need technical assistance with this concern, you can always reach out to our Customer Care Team. They have the ability to instantiate a remote-viewing session to help you through the procedure.
Of course, you still got me here in the Community if you have any other questions about this concern. Just leave a reply below and I'll get back to you. Thanks for coming and have a good one!