If some participants didn't get redirected to the correct completion URL, they'll be listed in your submissions with NOCODE, or you may see the wrong completion code against the submission.
NOCODE means that the participant completed the study manually and not via the completion code you provided.
This usually occurs for one of two reasons:
1) The participant reached the end of your survey, but were not redirected back to Prolific via the completion URL for some reason. Therefore, they had no way to access the completion code and had to submit without one, or instead submitted the wrong code.
These cases should be approved as normal if there is no issue with the submission; you should check your survey data to ensure that they fully participated in your study, and you can also use their completion time to gauge the likelihood that they did reach the end of your survey.
2) The participant decided to leave your study early, or could not proceed because of some technical issue. Instead of returning their submission, they have submitted without a completion code or with the wrong completion code by mistake, and appear in your 'awaiting review' list.
You can identify these cases by checking your survey data to see that they have provided incomplete (if any) data, and those that experienced technical issues may also have short completion times (i.e. a few seconds).
If you feel they do not deserve to be penalised with a rejection, we recommend that you send a message to these participants asking them to "return their submission" on Prolific or find out if they experienced an issue and would like the opportunity to participate again.
For more help with reviewing submissions, see here: Reviewing submissions - How do I decide who to accept/reject?