I unarchived my list but check list no longer displays - despite on list view it indicates checklist with 0/4 being displayed
This is not normal as restoring an archived item should restore all of its content, including checklists with 0/x elements checked.
I noticed that, sometimes, after restoring an item and opening it, the content takes some time to load (comments, checklist, attached files,...) so you could wait a bit or reload the page.
Maybe this is a display problem, you could try with a different browser or device, but that would be weird.
If it's still not working you should contact the Trello Support from the contact page (not the Trello Community), they are in the best position to help in that case. Even if you start inspecting the code and see a problem in the console for instance, you'll probably need to contact them.