I had this happen last year for some reason. I just went in to each Sassie for each MSC, toggled the Email Off to Email On setting in the upper left hand corner. And it never happened again. I do recall getting an email from one MSC saying they noticed I never opened their emails, so they were going to set my email setting to "no". This might have triggered it for others, I don't know...!
I've noticed weird things recently with Sassie email, regardless of the MSC. Sometimes I don't get the "accepted" emails until a day later for self-assign shops; sometimes I don't get them at all. I've had to keep a close eye on the shops I apply for because half the time I never get notifications when they're approved/accepted.
If your path dictates you walk through hell, do it as though you own the place. -unknown