This is going to be very difficult to answer. A bit like standing on a station platform trying to work out why your train hasn't arrived when the only information you have is its non-arrival. That's what's happening here. Your web browser is sitting waiting for the center panel contents and they simply don't arrive from your server, so we have no information to understand why.
All's not lost though.
We can see the point at which data stops arriving. That's after the breadcrumbs and any Zen Cart warning messages would have been displayed if there were any. There aren't so your problem is almost certainly a PHP error on your server.
Unfortunately it's in the code that constructs a variable called $body_code and that's about 2/3 of Zen Cart's code.
There are two things that you can do. Firstly, you can look at your front page and validate it. There are a number of errors there that are structural e.g. missing end tags. Fix these and you may stumble across your problem naturally.
Also, I suspect that you web host has PHP set up to suppress errors. Site's don't usually just stop without an error message. These messages, though cryptic, do tell you exactly where to look for the problem and are invaluable for debugging.I'd advise discussing with your web host, how you can enable them.
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(Questions answered in the forum only - so that any forum member can benefit - not by personal message)