Workers are Telling me they Cannot Take my Study. Why Not?

If you emailed a group of workers to let them know about one of your studies and a worker tells you they cannot accept the HIT, it may be for one of the reason below.

1. Mechanical Turk only allows Workers to accept a HIT one time
   One feature of MTurk is that a Worker ID can be only be associated with a HIT one time. This means if a Worker accepts your HIT and then abandons it or runs out of time to complete it, they cannot accept the HIT a second time to try again.
   Sometimes, workers who tell you they cannot accept a HIT may have completed the study and accidentally re-selected the HIT thinking they have not completed it yet. To check if the worker has already taken the study, you can inspect the Worker IDs in the .csv file associated with your study.
   At other times, workers may tell you they cannot accept your HIT after you have emailed them because the worker accepted the HIT before you sent out the email and does not realize you are emailing about the same study. This happens when workers find your HIT organically on their dashboard before receiving an email about it.
   Finally, a worker may be unable to accept your HIT if they try accepting it before Amazon assigns the Qualification to them. In this case, the worker simply needs to wait a few minutes for the qualification to be assigned and then try again.
2. The Worker may no longer be qualified for the HIT
   If you run a study and select workers with specific criteria that are subject to change, like approval ratings, it is possible workers will tell you they cannot accept your HIT because they no longer have the qualifications needed. For example, your initial study may have required an approval rating of 95% and above. If you selected the same qualifications for your second study a worker whose approval rating has slipped to 94.5% would be ineligible for the study.
   Because studies with an Include list typically seek to contact all the participants sampled previously, we recommend not adding any qualifications to follow-up studies. Whenever you use an Include list, the only people eligible for your study are the ones on your Include list. In cases where workers on your Include list tell you they were unable to accept your HIT, you will have to launch a new HIT for them after removing all qualifications.
   If you did not select any criteria for your follow-up study but are still getting emails from workers, please email your study ID and the WorkerIDs to CloudResearch support at support@cloudresearch.com.