If it's for Market Force, they only allow so many of the same shops for the same client in a particular radius within a time span. Basically, you can only do a few of each shop so many miles apart and so many days apart. If you did a burger joint on Tuesday, maybe you could do another on Friday in a town just a few miles away but you probably wouldn't get the same burger joint on Wednesday unless it was close to the end of the month. Even if you can see the shops, they may not have updated yet after accepting others so you get the error message telling you it's no longer available to you. Now, on that note though, if you write down shop numbers and send help desk a message or give a scheduler a call, they may make an exception and assign you. I spotted some shops I wanted and accepted one but the other went poof. They were make offers so I knew it was that time... I sent a message with shop numbers and ended up getting all three because I did them that day for the new $20 base.