A rejected shop is no reason to quit mystery shopping altogether. Most companies will not just outright reject a shop. They will ask for clarification on your responses and, possibly, some tidying up of your narratives. If you lied on a report, and there is video evidence at the location shopped, you may be in danger of a flat out rejection. Other than that, most companies will give you a chance to revise and resubmit your work.
A rejected shop is not the end of the world, and not even the end for conducting shops for that particular company. You can contact the editors and/or schedulers to get specifics about why the shop was rejected and how you can improve the chances of your next submission being accepted with no questions asked.
Companies are in need of good, reliable shoppers and are usually eager to groom new shoppers into who they want conducting shops for them regularly. The most common reason for a mystery shop being rejected is not following the guidelines and instructions given for conducting the shop. This is why it is so important to read over all directions, guidelines, and report forms before you do the shop. If you have any questions, contact your scheduler before you complete the shop.
If you shop outside the prescribed time-frame, your shop will be rejected. That includes time of day, as well as actual day or date shopped. If you fail to shop the correct department or correct person, your shop will very likely be denied. With a target shop, sometimes things come up when on-site that make the target unavailable. Ask your scheduler what to do in these instances before you conduct the shop.
Rarely are poor reporting skills used for rejecting shops entirely. The option is given to work on the narrative, or the shop may be accepted and you will receive a lower rating with that company. If you receive a low rating, contact the editor and ask for helpful hints and ideas on how to improve your rating. Again, they are usually quite willing to help you do a better job as it makes their job easier also.