clicking on export to csv gets me error 500 (unable to handle req) on form 1of2

this wordpress site has 2 forms of this plugin, it was working fine, out of no where got this problem – when i click on export to csv it shows error 500 This page isn’t working www.a1hometutors.com is currently unable to handle this request. but, if i talk about the second form of this same plugin of this same website, is working fine, i am able to export to csv for that form but not of this form, it was working fine around 2 days back.
the link i provided is of the plugin – messages page, website – a1hometutors.com, 2 forms – student (working fine) – https://www.a1hometutors.com/student-registration/ . tutor (problem) – https://www.a1hometutors.com/tutor-registration/
Pl Help!