Terms and conditions article not showing in popup

The terms and conditions popup is not displaying. Clicking on the link in ' I accept the  Terms and Conditions ' displays the dark overlay but the article does not display. I don't know when this stopped working but I changed the joomla template a few months ago to one I created in Nicepage but I don't know if there is some incompatibility here.

I see there is a previous post that seems to be this same issue but that was over four years ago:  Blank Terms and Conditions Page - Joom Donation - Joomla Extensions by Joomdonation

The poster there said:

I noticed that If I load without the "?tmpl=component&format=html" the article opens fine in the popup.

and:

 tmpl=component if I remove this from the URL the article shows up

...but I can't see any way to do this. How can I remove this when all MembershipPro allows is the article to be selected?

I tried Tuan's suggestion in that thread about linking the terms and condition article to a menu item (I temporarily used my existing footer menu rather than creating a hidden menu) but this made no difference.

Any idea how this can be fixed or perhaps a way to get the terms and conditions article to display in a new tab rather than a popup?

The page on my website is:  www.healthsense-uk.org/component/osmembe...-up.html?Itemid=1370

Hello Alan

For this, better submit a support ticket sending us super admin account of your site and link to the page which we can see the issue

We are going to check to see why the issue happens and get it sorted

Regards,

Tuan