Please accept my sincere apologies for the delay getting back to you. I’m afraid that your request for assistance was missed by the support team, and it’s only now we’ve been able to work through the backlog of older discussions.
Would it be possible for you to attempt to connect again by first creating a new empty file and then adding the account again?
To do this, you will need to open Moneydance and click on File > New > Create New File, then select the empty checking account from the sidebar and click on Online > Setup Online Banking, enable automatic downloads in preferences, restart Moneydance and let me know if you are successful with the empty file.
It took me almost a year to make any progress with this, but another issue forced me to restore from backup. As soon as I did that, sync was broken (different issue that I'm not trying to support here). To fix syncing, I used Derek Kent's excellent instructions and script to make my laptop with the backup file the master. As soon as I finished restarting MD, the transactions auto downloaded. When I re-set the additional slave systems to sync with my new master laptop, they do not auto download at startup even though the preference is set..
In short, it seems that when using Shared Folder sync, only the master can auto-download transactions at startup. The slave computers can manually download transactions, but their auto-download doesn't work no matter how the settings are configured. It's probably an unintended consequence, but I wanted to share it with the public in case it helps anyone.
Currently on Windows 10 2019.4 (1888) on the master laptop.