Hello Eric !
When you’re here, open the System Preferences, then Security and Confidentiality (Sorry, I’m a French user, I’m not sure of the English words…). Click on the lock down left, enter your password to unlock it. When done, you can click on “OK” below in the message “Navigraph cannot be opened, bla, bla, bla”. Now you should see a new line in the System Preferences, ending with “Open Anyway” or something like this. Click on this, then relaunch the FMS Data Manager. Now, you should have the same warning window I posted previously in this topic and be able to open it. By the way, I use the same procedure with the new add-ons which contain the “mac.xpl” file, e.g. a new aircraft.
Please tell us how far you go after that !