Check and correct virtual tour problem using PTGui. (This software only)

I've just shot (in HDR) and stitched a single 360 degree panorama using PTGui. The HDR is fine, the colours look gorgeously vivid without being excessively unrealistic. I currently don't have software for multiple pano tours, and need to concentrate on just this one 360 as I have a problem. Help please. I'm using Windows 10, very fast processor and normally Google Chrome. For upload I'm using Filezilla onto my own server. The panorama displays correctly in the PTGui viewer offline. Google Chrome won't display the 360 pano offline. OK no problem there if they don't want to. I have my own server. I've uploaded the four HTM files and the associated JPGs, shockwave and JS. I put the address of the first HTM file into the browser and I get what starts looking like a virtual tour ... except one quarter of it is totally missing. It all still fits together seamlessly, but gives the appearance of disappearing off into appears to be the infinite depths of deep space. I've looked through the HTM file and can't see anything missing. I've tried both Chrome and IE both with up-to-date versions. Can anyone suggest where I start looking please? Please: 1. Fix the problem using PTGui; 2. Confirm to me the correct settings in PTGui for future work (that I will do); 3. Provide a clear account of the fix to the problem in UK English. FYI I am using PTGui Pro v 10.0.15 I'll supply a zip of the complete 360 degree panorama HTM, JPG, JS and SWF files as it stands to the chosen bidder. The 360 is of a street scene. Many thanks