Most likely, the emails you received went out to many, many shoppers and you were not the only one to respond. The scheduler simply assigned them to other shoppers, making them unavailable to you - and not visible on the job board.
You wrote your concern at the end of a month, when schedulers are trying to meet deadlines. The least likely time for a new shopper with a company to get selected is at the end of a month. A huge percentage of new shoppers take shops and then never perform them. When deadlines approach, schedulers cannot afford to have any more "flakes."
Schedulers are usually independent contractors like we are and do not get paid for polite "sorry, I can't schedule you" responses. So, don't count on responses when you are not offered a shop. Be courteous and professional. Persistence will pay off.
Primo solutions is a legitimate company. Keep trying - you'll get selected at some point. Try requesting shops both online and through email as soon as they are advertised. When asked for a date that you will perform the shop, choose the soonest possible date.
Hard work builds character and homework is good for your soul.