Have you tried e-mailing any of the schedulers for any of the jobs for which you've applied? I've only been with them a very short time, but have found the schedulers to be very responsive and willing to, for example, assign a shop to a relatively new shopper who doesn't yet have the required rating.
I really like this MSC so far! I think you'll at least get a personal response if you e-mail somebody. Not sure they can tell you the reason why you're not getting shops, but they do respond to e-mails. Good luck!
I learn something new every day, but not everyday!
I've learned to never trust spell-check or my phone's auto-fill feature.