Hello & Welcome to Just Answer,
Sorry I didn't see your question earlier and to hear of any trouble.
When you mention that you "lost connection, immediately after completing the download", that has me a bit concerned that ALL of the files for the maps MAY NOT have been completely written to the memory card.
So may I ask of you performed the "safe removal" of the card BEFORE physically removing it from the computer or card reader?
NOTE: The "safe removal" process is where you "eject" a removable media device from the computer - before physical removal.
Also, did you check the Map Information screens on the device, once the card was installed, and make sure the new maps were seen by the device AND "enabled"?
As a reference, I have a link to a video that shows how to install "pre-programmed" microSD card on these devices, and check the Map Information screen.
Click here -->https://www.youtube.com/watch?v=fD6L91YMJSk
Note: The maps shown on the video are NOT for South Africa, but the concept is the same.
If the maps can NOT be seen when the card is inserted, you MAY have to do the download to the card again, making sure to use the Safe Removal process at the very end.
Please let me know what you find or if you have more questions.
Thanks, ***** *****