We found out it's an internal issue and we have communicated it to IT- thank you! 

In my case it turns out we are having an internal email issue and it's NOT related to WF. Though for future reference the first place you will want to check are you setting and make sure you are receiving instant emails and messages to tags, request, approvals and so on.  Good luck! 

Lately a number of my team members haven't been recieving their email notifications when they are tagged in a project. Is anyone else having an issue with this? How have you been able to resolve it?