I am using a custom allowlist pre-screener, but after more than 2 months, now I have collected only 82% (still many missing participants between returned and timed-out),
My question is how to get my full submissions (increase/add more participants, as it requires more money) or get my money back?
While Prolific has already deducted the total amount, those targeted participants (returned and timed out) will not get paid.
Welcome to the forum
I guess you did a custom screener to find participants to suit your study. Prolific estimates I think (or at least I have estimated here on these forums) that not everyone will come back so you need to find between one and two times, I have guessed at 1.5 times the number of participants you finally need or 1/1.5 which is 67%, so in my humble opinion a return rate of 82% is very good. Prolific offers no guarantee that participants who matched your criteria and are on your allow list will in fact come back.
Prolific ties up the funds of studies while they are active but once the study is completed the funds that were not given to those who timed out and returned their submissions will be returned to your account.
So what can be done. Some suggestions…
You can wait.
You can stop your study and re-release a copy to get the participants on your allow list to be invited again.
You might consider explaining the significance of the study more.
You might consider paying more (though it could be argued to be unfair on those that have already taken the study, and introduce a confounding variable)
You could prescreen for some more participants that match your criteria but bear in mind that only 66% - to 82% of them will come back to take your study proper.
I hope that helps a little,
Thank you so much for your helpful reply that answers many overwhelming questions that kept me awake for a couple of weeks, really appreciate your support.