Participants are receiving a fatal error message when entering the authorization code to enter a survey. What does this mean?

Question

When participants are inserting their authorization code to enter a particular survey, they are getting the following message: Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 16777224 bytes) in /var/www/soscisurvey/html/inc/functions.php on line 922.

How can I resolve this issue? What does this mean?

Comments

It seems that this error is not related to the authentication code (serial number), but to something within the questionnaire, probably on the first page.

Could you please specify the name of the questionnaire (you have several active projects in your account) where the error occurs? Do you use any PHP code on the first page? If yes, could you please post the PHP code?

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PS: I have creates an administrator access for the first project (20182), and created 20 test codes. Seems to work properly when I open the URL and enter the code. Therefore, I assume, a specific project causes the problem.