I'll chime in and share my thoughts about why you're getting this error.

As far as I know, the QuickBooks Desktop 2020 software discontinuation is after May 31, 2023. It includes all 2020 versions of QuickBooks Desktop Pro, QuickBooks Desktop Premier, QuickBooks Desktop for Mac, and QuickBooks Enterprise Solutions v20. Other Intuit products are affected by the software discontinuation.

Part of the discontinuation is the unavailability of manual bank import. That said, you're getting the error because the QBDT Mac version is not supported anymore. You can visit this article for more detailed information: QuickBooks Desktop 2020 service discontinuation policy. Although this link is for QBDT for Windows, the same concept applies to Mac.

If ever you upgrade to a supported version and the same error occurs, you can check out this article to learn how to fix it: Fix error OL-222 in QuickBooks for Mac.

Feel free to post here again if you have further QuickBooks-related concerns. We are available 24/7 to lend a hand with each of your queries. Stay safe!