There are multiple possible causes of the case. I checked the backend of the website and found out the JS error. The error indicates that the dropdown of the demos can not get the list of demo content and that shows you can not connect to our server to get the demo content list from your WordPress installation, and/or there is not enough PHP memory limit to be able to get the information.
I went o X > Status and checked the server information of your installation. The first thing to do is to increase the PHP memory limit to 512M and here is hot to do so:
Kindly, contact your hosting service provider if it is not possible for you to increase the memory limit yourself.
I would also encourage you to contact your hosting service provider and ask them to make sure that it is possible for the WordPress installation to contact
https://theme.co/ and all its subfolders.
Finally, I would rename the X folder in the themes folder of my WordPress installation and would try to install a new version again to rule out any corrupt installation problem.