Make sure both computers are running the same version and build. Update your old computer to the latest build if required.
To copy your data set to a new computer, proceed as follows.
On your existing computer click on HELP – SHOW DOCUMENT FOLDER. This will open a file explorer in the default data set location.
Close Moneydance. Your data set is a folder not a file containing other files and folder. I think it’s called a bundle on a Mac. The naming convention for the data set is yourdatasetname.moneydance. Copy this folder.
Open Moneydance on your new computer. Assuming this is the first time you have opened it; it should open in the welcome window Click “Account a new account set” and set up a dummy account so you can then click HELP – SHOW DOCUMENT FOLDER. This will open a file explorer in the default data set location. Close Moneydance. Paste your data set is to this location.
Open Moneydance then FILE - OPEN (MONEYDANCE – OPEN on Mac), your data set should be listed.
Use the same key to register Moneydance.
To ensure auto backup is working under PREFERENCES – BACKUPS. From time to time check new backups are being created.