500 Error on membership 2 Free Registration

hello I am having an issue with a 500 error when someone tries to register on Membership 2 plugin.

this is the link that gives me the error - https://figtreelive.com/register/?step=process_purchase&membership_id=9994&ms_relationship_id=18190&gateway=free&_wpnonce=f63403474b

it says this
figtreelive.com is currently unable to handle this request.
HTTP ERROR 500

Any ideas on what might be causing this? I can toggle on support if you need to login

thanks for your help!
Cody