This can sometimes occur for a couple of reasons. Either the participant clicked your survey (before you sent out the email to them by seeing it on their dashboard organically) before Amazon assigned the Qualifications to them, or the participant accidentally clicked into the survey without realizing and then either closed it or had some kind of accidental glitch occur.
Participants may have also completed the study and accidentally re-selected the study thinking that they did not yet complete it. To check if this occurred, you can search the workers ID in the CSV file.
To see the exact reason why workers aren't qualified, we'd need the worker ID's of the workers who reported they were not qualified and we can take a look for you. We would also need the survey ID for the study that the workers should have been qualified for.
Unfortunately, due to the measures we take to prevent duplicate responses, the only way to have these participants take the survey would be to turn off ballot stuffing (if it isn't already turned off) on your survey file and send them the link directly (not through TurkPrime). You can then open up compensation HIT on TurkPrime to compensate them. Please see our article on opening up compensation HIT's for more details.