I sent you the template earlier on and you replied it worked for you and suggested I re-install lightbox.
This I did but encountered initially another problem in that I didn't get the registration validation screen and so clicking on the lightbox icon in DW did nothing. Deleted the .mno file associated with this and for good measure deleted the winfilecache-xxxxx.dat file and restarted DW. This time I got the registration validation screen entered the serial number etc. and lightbox was available after another restart of DW.
I then tried to create the page again using a smaller number of images (there were 67 in the original batch) and had the same problem when adding the HTML5 Slideshow extension with lightbox.
I then took a video capture of the screen whilst I re-produced the problem and that file is currently uploading. I will send the link in the morning.
However there is a development. When I subsequently selected the HTML5 slideshow object on the page and then in the properties inspector clicked on slides to re-open the extension dialog, made a small change and then clicked on OK this time the code for the lightbox seems to have been added and (I think) it works as planned. I say I think because I can't navigate between images whilst in lightbox.
When I do get this working as expected I will be re-doing the template as with all the messing around with code I seemed to have affected the CSS Navigation and I want to integrate a comments system on every page.