Member unable to view calendar

I have a curious problem to try and solve.The calendar (LuxCal 5.1.1) on our website works perfectly for me and most of our members, but one member is reporting the following issue:

"When I use my wife's iPad (Safari browser, I think) I can view the calendar. When I use my laptop, whether on Chrome or Microsoft Edge, all I get is a technical looking page saying 'click this header when done', with a column of boxes down the side, which I don't seem to be able to get away from."

I haven't actually seen how the calendar is displayed on his laptop and I'm not sure I quite understand the description. I have asked him for a screenshot. Meanwhile does this ring any bells with anyone? I guess the issue is to do with something wrong on his laptop, but I have no idea what that might be at the moment. I have searched the forum for 'click this header' and 'header', but no posts are shown.

Edit: I have managed to replicate the problem. I use Firefox, and the calendar renders perfectly in that, and in Safari. But in Chrome and Edge it looks as though the CSS (and maybe more) is missing. I am sending Roel a screenshot.

Edit2; SOLVED. For the benefit of anyone else with this problem it was due to the fact that the calendar comes from a secure site and our website was not secure; it was using the h t t p prefix rather than  h t t p s. To ensure that anyone who had bookmarked the h t t p link was properly redirected I added five lines to the htaccess file in the root folder of the site. If you need the code, you will have to ask Roel; I am prevented by the rules from posting it here.

Thanks, as always, to Roel for his invaluable help.