OK, so the problem is that there's a change in CKEditor in Blesta 5.0+.
The HTML code that launches the descriptions are removed by CKEditor when you go into the package.
In the package description, the following code is appended to the text of the description:
$viewmorelink = "<a class='mod_view_more' href='javascript:void(0);' onclick=\"window.open('$sslfeaturelink','null','location=no,toolbar=no,menubar=no,scrollbars=yes,resizable=yes,addressbar=0,titlebar=no,directories=no,channelmode=no,status=no');\"> View Full Product Details</a>";
To fix it, you need to wrap the <a class=...> ... </a> in the following:
<div class="raw-html-embed"> .... </div>
Or just make sure you're using the "Insert HTML" block for that set of code.