I'm wondering if it's a connection problem to ECT - when you log into your store admin does the store version show or do you get a message about not being able to connect to ECT?
Can you ask your host to update the PHP version on your server - PHP5.6 might be best at the moment but if you get a newer version of ECT then you can go to PHP7.x
If you switch to PHP7 make sure you have the correct syntax in db_conn_ope.php and includes.php (you probably do) https://www.ecommercetemplates.com/support/topic.asp?TOPIC_ID=107737