Booking form gives post error

[ShopemParticipant]

The booking form gives 500 error;

 

jquery.min.js?ver=3.6.0:2 POST https://xxx.nl/wp-admin/admin-ajax.php 500

send @ jquery.min.js?ver=3.6.0:2

ajax @ jquery.min.js?ver=3.6.0:2

s.ajax.s.ajax @ jquery-migrate.min.js?ver=3.3.2:2

S.<computed> @ jquery.min.js?ver=3.6.0:2

(anonymous) @ pixcars_reserv.js:278

dispatch @ jquery.min.js?ver=3.6.0:2

v.handle @ jquery.min.js?ver=3.6.0:2

[Support teamKeymaster]

Hi.

Please, give me the site url and admin access.