I have never tried this so cant confirm that will work. TRY IT AT YOUR OWN RISK. But it sounds like you have little to lose.
Recover data from the “.moneydancesync” folder in Dropbox Moneydance 2017.
In Dropbox make a copy of the folder “.moneydancesync” with a different name and store in a safe place.
In Moneydance click FILE – NEW – OPEN SYNCED FILE. Use the dropdown to set the same sync method as you were using. Enter the same passphrase as before and start syncing. If your data set is synced back into your computer you may need to tidy things up. Particularly the things listed in the side bar. Use the “+” at the bottom. You will probably find under FILE – SYNCING that you can’t set a syncing method so you need to convert your data set as below.
Create a backup using the FILE - EXPORT BACKUP.
To use the file md2017_convert_secondary_to_master.py, first download it to your computer and then follow these steps:
In Moneydance, select Window --> Python Scripting.
In the window that opens, select 'Open Script' then navigate to the .py file wherever you saved it on your system.
Select 'Run' to execute the file.
Wait a few moments until you see a message on screen, confirming the script has run successfully.