Certain web applications like Salesforce try to open new windows in your browser. If you're having problems with new tabs or windows opening. Try the steps below!
1. On your Mac, open Safari
2. Click Safari from the top menu bar then Preferences..
3. Choose Websites from the options listed
4. Then along the left hand side menu, choose Content Blockers
5. For the setting on the bottom right "When visiting other websites" toggle this to Off
It's a good idea to close Safari completely and open it again.