Welcome and thanks for dropping by the Community, @cain_oliver229-y.
The browser's cache and cookies may be causing these unusual responses. To isolate this, try signing into your QuickBooks Self-Employed (QBSE) using a private browser (incognito).
Once logged in, try to connect the bank again to double-check. Here's how:
If it's successful, return to your default browser and perform a clear cache to refresh the system. However, if the issue persists, try using other supported browsers.
To learn more about managing bank transactions in QBSE, refer to this article: Create rules to speed up reviews in QuickBooks Self-Employed.
Please leave a comment below if you have any other questions or concerns. I'm always here to assist. Have a good one!