Some firewall and antivirus programs sometimes block Sync from working properly. Here's how to add Sync as an exception in Bitdefender for Mac:
Adding Sync to the Allow list in Safe Files
- Click on the Bitdefender icon from the Menu bar then select Preferences.
- From the Bitdefender console, go to the Safe Files tab
- Click on Manage Applications
- Click the + icon at the bottom-left corner of the screen to add an application
- Ensure Applications is selected from the sidebar then select Sync from the list
- Click Open
- Under the Action column, click on the arrows beside Blocked
- Select Allowed
- Click OK