Market Force does, indeed, restrict what newly signed up folks can see. (I am talking about the 'blue portal' that used to be Shop 'n Chek, not the 'purple portal' of Market Force that is/was Certified.) Once you have done a few shops for them in a timely and complete fashion you are likely to see 'better' jobs. There are some attitude problems with Market Force that you do best not to get tangled with. One is the mention to them that their website is flaky. They will deny it and I'm sure put you down somewhere as a 'complainer'. (I've been around computers long enough that when a website does the same flaky thing with several different browsers and using several different machines, I know it is not my problem but theirs. So wait a few hours and try again. Chances are there will be some naive soul who will complain, take the hit and insults while they repair the site.)
For some reason Market Force seems to get a little mixed up on its shopper lists. A friend got a little bent when he got a 'congratulations on completing 250 shops' email when he has done more than 1500 for them. Meanwhile he was getting banned from ff shops because the receipts he received were too light to darken adequately for proper submission. Other long term shoppers have had other issues with them and the more you seek justice, the more shops you get excluded from.
I find that the best way to deal with them is to keep my head down, self select what I want, when they call indicate that a shop I don't want 'won't work with my schedule--maybe next time' and don't get too involved in bonus negotiation. If what is offered is not enough, it 'won't work with my schedule'. If the website isn't working, try again later. If the website is limping, keep making my upload a smaller and smaller and smaller file until it goes through.