The requester makes the decision, and unfortunately, there isn't much you can do. A lot of requesters will have tests or post HITs without qualifications, then add the qualification to those who do well.
Hi, I am fairly new to Mturk.... Where can I find a thread or info on being rejected for a qualification? Who makes the decisions? Specifically, I applied for English - German native translations and was rejected... how can I find out why (no reason was given). I'm confused!