I have 2 employees that are in our seed list and they aren't receiving emails. I'm having to go back and add them into the database each day. Why on earth are they disappearing?
since when they are deleted, you cannot look at their activity logs. Ask support, they can undelete them for you and might be able to tell you how they were deleted.
Are they non-existent in the database when you go back to add them? No record of them, etc? It's possible they've gotten blacklisted somehow.