The error message:
This error says two things:
a. server responds with status 500
Please contact hosting to confirm what that means.
b. JS error in wordpress files (wp-admin/admin-ajax) That is wordpress file and if wodpress errors show can be several causes (but it’s not theme for sure as for us everything works fine)
This is related to the server configuration.
To solve it – install php5-url (original link with the solution) https://wordpress.org/support/topic/plugin-ajax-fo…
Other issues related to 500 Server Error can be limited resources allocated for your account. If you get this error when you import demo see this help – https://help.wpresidence.net/article/demo-content-1-click-import-starting-1-15-update/#c_wpestate_id