Whole page sections are missing after moving Gridbox sites to new web host

I'm moving from one web host to another, and migrating my Gridbox sites.

I have the old host running Joomla 3.x and have installed Joomla 5.x on the new web host. In Gridbox on the old host I'm exporting the site and then importing into Gridbox on the new host, (I'm having to manually rebuild the Galleries because they're not exportable - bummer, and move images manually.)

When I view the site on the new host, whole sections are missing (for example, a Content Slider, a Carousel and a Testimonial Slider on the home page). But, when I go through the Administrator back end to edit the page, those three sections show up in edit mode.

What am I missing or needing to do to get these sites to migrate fully?

Thank you!