If you are prompted to log in to your Contacts+ Mac app each time your MAC OSX device is restarted, something might be off with the KeyChain access on your Contacts+ Mac app.
Please check KeyChain for `FullContact Authentication`and if it has an entry for Contacts+ under Access Control.
Please find the following .gif file with the procedure followed to make sure that the FullContact entry doesn't show up on KeyChain access:
If you see 'FullContact' instead of 'Contacts+' (as shown in the .gif file), please open the `FullContact Authentication` with the right-click (two-finger tap) -> Get Info. You just have to delete the 'fullcontact' entry from the KeyChain. That should do the trick! You don't have to create a new entry for Contacts+ as it will happen automatically. So, once you delete the fullcontact entry, you should be all set.