Is the url correct in step5 export project?

Could it be that https or http is not correctly set?

Is the PHP version correct for the server that does not work? use 7.1 or 7.4

Check the FAQ, maybe the rules are different for sending forms (mail) from server.

Other providers can have other rules. Best way to chack is to use the admin panel in x5, and again check the FAQ of your provider on rights for sending mail / email forms from there webserver (that's what the form of x5 needs)

Test in admin panel, set / admin behind your website URL, login with password that you can find in x5 step1 -> advanced -> user acces. Go to test section and try several scripts or send options, set them to the same as in the FAQ from the provider.

https://guide.websitex5.com/en/support/solutions/articles/44001791318-what-are-the-minimum-requirements-for-the-server-

https://guide.websitex5.com/en/support/solutions/articles/44000618332-website-x5-online-control-panel-