I appreciate you for coming back to the thread and adding confirmation about the version of QuickBooks Desktop you're using. With this, let me discuss further details on how migrating your data works in QuickBooks. Then, ensure you're able to transfer your file by performing some alternative ways to achieve your goal.

When you migrate data from QBDT to Online, you'll have to ensure that you use the same international version. Since you've mentioned that your company is in South Africa, this is currently discontinuing our Desktop offering in the said place. 

Additionally, we have to temporarily hit the pause button on all QuickBooks Desktop to QuickBooks Online migrations, starting on June 16. This means that we won't be able to help you transfer your QuickBooks Desktop data over to QuickBooks Online. 

However, you can look for a 3rd party app outside QuickBooks that will allow you to convert your data from QBDT to QBO. Also, you can still manually move your data across using the Excel CSV files. This way it helps you transfer your data from QBDT to Excel and import it to QBO.

On the other hand, we'll update this space as soon as the new and improved migration process is back online. Then, rest assured that the new migration process will allow you to move larger files with no size limitations.

Lastly, I'm adding this article to further guide you in effectively managing your business using QBO: Help guide for QuickBooks Online. This contains topics about different accounting strategies, banking, and payments.

Get back to me here if you have further questions about migrating your data in QuickBooks. I'd be more than happy to answer it for you. Have a nice day!