Hi vicente,
Thank you for your purchase.

Sorry for inconvenience,

Please provide me a temporary WP-admin login for your site where this happens, so we could log in and take a look ‘from the inside’ as that’s the most efficient way to see and resolve the issue. We do not interfere with any data or anything else except for the plugin (in case that’s a production version of the site), and of course we do not provide login data to third party. You can write credentials here just check Private Reply so nobody can see them except us.

Also point me on table id, so I can take a look and id of the form

Hi vicente,

Yes we found what cause the issue. There are some Warring messages that are been shown in Ajax response and break it as well and that is the reason why you get this error. Issue is on our side and there is fix for thatYou can change it in file

 wp-content/plugins/wdt-gravity-integration/wdt-gravity-integration.php around line 615

you will find this

if (self::$wdtParameters['sortable']) {

and you have to replace with this

if (self::$wdtParameters != [] && self::$wdtParameters['sortable']) {

also in same file around line 680 you will find this 

$aColumns = array_keys(self::$wdtParameters['columnTitles']);

and you have to replace it with this

$aColumns = (self::$wdtParameters != [] && self::$wdtParameters['columnTitles'] != null )?  array_keys(self::$wdtParameters['columnTitles']) : [];

This will be included in next update so you don't have worry about that,

Sorry for inconvenience,