[Resolved] 500 Admin-Ajax Error on Form Submit

I am passing expert match id as a URL param and using it to store data in custom tables using cred_save_data. It all worked just fine earlier when I was not using Ajax on the form. But, when I enable ajax, the URL param was not recognized by the form or by the custom code in cred_save_data. That created a null error and stopped the code from executing. Is this expected behavior?
I'm not sure, it depends on how you are passing that URL parameter into the Form, and how you try to access that URL parameter in the cred_save_data hook. Are you using the URL parameter to set the default value of a field in the Form, or using $_GET or the PHP referrer somehow to access the URL parameter somehow in the cred_save_data hook? Please explain the flow of URL parameter data from the page containing the Form to the cred_save_data hook. If you're using the expert form builder, please include any shortcodes that reference URL parameters. If you're using the drag-and-drop form builder, please include screenshots of the field settings for any fields that reference URL parameters. Please include the cred_save_data hook you mentioned so I can see the failing code.

2021-03-17 12:36:10 UTC [nginx][error] 53783#0: *2590393 openat() "/home/u742-0y1sfigedrww/www/showprowess.com/public_html/.well-known/pki-validation/ca3-ea095c7c2a684678852f2c43520f440d.txt" failed (2: No such file or directory), client: 172.69.27.83, server: showprowess.com, request: "GET /.well-known/pki-validation/ca3-ea095c7c2a684678852f2c43520f440d.txt HTTP/1.1", host: "showprowess.com"

I'm not convinced these errors are related, this issue seems to be related to certificate validation in HTTPS sites. The .well-known directory is usually created during domain validation.

6) The code in the hook uses $_GET['expert-match-id'] to get the id
I would not expect to find the form parent page's URL params in $_GET in a cred_save_data hook with AJAX. With AJAX, the processor URL is admin-ajax.php and none of the URL params from the parent page are automatically passed along. Without AJAX, the processor URL is the same as the page containing the form, including existing URL params.

For consistency in either AJAX or non-AJAX submissions, you should access the related post ID in $_POST using the following syntax:

$_POST['@expert-match-to-expert-review_parent']

Note that the "." character in the field name is replaced by an underscore, this is expected.

...When I use ajax form submission, the form submits and the post is created but no relationship is formed between expert match and expert review post type
After form submission, and after the cred_save_data hook has run, I expect the relationship between the parent post and the new child to be created automatically. Can you confirm a form_messages field is included in the Form builder?

[cred_field field='form_messages' class='alert alert-warning']

If not, there may be an error returned by the Form submission but not displayed obviously. You should replace this field if it was deleted. If that is not the issue I'll need to take a closer look. Please provide login credentials and show me how to get to the child post Form on the site.

Also, the code in the hook does not run...
As I said, I expect $_GET['expert-match-id'] to be null in an AJAX submission, so logically the conditional in the cred_save_data hook would prevent most of the code from being executed. You must use the $_POST['@relationship-slug_parent'] syntax instead of the $_GET syntax.

...and the user is not directed to the post
See above about the form_messages field, that could be related to what you are experiencing. Or if not, what redirection settings are applied in the Form editor for the child post Form? Do you have a cred_success_redirect hook implemented for this Form? Even if you have a custom redirection hook, you must select one of the redirection options in the Form settings to redirect to some different location than the original page containing the Form. Otherwise the hook will not work.

Is the expert review id created AND post relationship formed by the time we run cred_save_data and cred_submit_complete?
The expert review ID is essentially $post_id, available in either hook as the first callback parameter. The post relationship is not yet created for cred_save_data, so you cannot use toolset_get_related_post or toolset_get_related_posts to retrieve information about the related post in a cred_save_data hook. However, the post relationship should be available in cred_submit_complete, so you can use toolset_get_related_post or toolset_get_related_posts in a cred_submit_complete hook. In other words, the post relationship is established in between the cred_save_data and cred_submit_complete hooks.