Thanks for bringing this one to our attention, DeepSouthT.

I also appreciate you for performing some troubleshooting steps to get this sorted out. I've checked here on our records and we have an ongoing investigation where customers encounter banking Error 102 when connecting to Nedbank. Our engineers are working together to get the permanent fix of this issue. In the meantime, we can get transactions from your bank and manually import them into QuickBooks Online (QBO). Here's how: 

1. Sign in to your bank or credit card's website.
2. Follow your bank's instructions for how to download CSV files of your transactions to your computer. Every financial institution has different steps.
3. Check the date range for the download. It should be at least one day before the date of your oldest transaction.
4. Download your transactions. Save the file somewhere you can easily find it, like your computer's desktop.

To learn more about this one, see the Manually upload transactions into QuickBooks Online article. Once done, please contact our Customer Support Team for them to add you to the list of affected users. Then, you'll receive an email notification once there's an update of this banking issue. Here's how:

1. Go to the Help menu at the upper right.
2. Select Contact Us.
3. Enter your concern.
4. Click Let’s talk.
5. Choose Start a chat. and type in your contact info.

Visit our Banking page to learn more about managing your bank transactions in QBO.

I'm just one click away if you need a hand with creating a bank rule or any QBO related. Just reply on this thread and I'll be sure to answer them. Take care always.