SimpleViewer is predominantly a Flash image viewer with an HTML fallback for mobile devices which do not support Adobe Flash Player.
Unfortunately, it looks like Adobe have discontinued support for Flash galleries in Lightroom 6/CC which seems a little strange being that Flash is an Adobe creation. I would have thought they would at least have kept Flash support for backward compatibility.
I could find very little on this subject online other than this Adobe forum thread: https://forums.adobe.com/message/7495493#7495493
I have done some investigation of my own and it appears that Lightroom fails to list a Web Engine in the Layout Style section if it has the following term in its galleryInfo.lua/galleryInfo.lrweb file: galleryType="flash".
If the galleryInfo file is not compiled, then you could force Lightroom to list the Web Engine by setting galleryType="lua" but the Web Engine would simply fail to function. Adobe appear to have removed all Flash functionality from Lightroom 6/CC.
If you want to continue to create SimpleViewer web galleries with Lightroom, it looks like you will need to use the last version of Lightroom which supported Flash galleries (v5.7.1).
Thank you for reporting this problem. I have notified the developers of SimpleViewer although, unfortunately, there is nothing we can do about this.
Incidentally, we did not write the TTG SimpleViewer Lightroom plugin ourselves and it was always offered free as a convenience for SimpleViewer-Pro users who used Lightroom. The current version can still be downloaded from the author's web page here: http://wiki.theturninggate.net/doku.php … mpleviewer
In light of this, you might like to try Juicebox. Juicebox is an HTML 5 image viewer which does not use or rely on Adobe Flash Player at all.
You can download Juicebox-Lite from this web page and you can then install the Lightroom plugin (which is included in the Juicebox-Lite download zip package) by following the instructions on this web page.
More information about the differences between SimpleViewer and Juicebox (along with details of a discount off the price of Juicebox-Pro for SimpleViewer-Pro users) can be found in this SimpleViewer blog entry.
Please note that the Juicebox-Pro Lightroom plugin has support for all the Juicebox-Pro configuration options. Please see this Juicebox blog entry for details. (The Juicebox plugin for Lightroom has been tested with and is fully compatible with Lightroom 6/CC.)
It is also possible to convert existing SimpleViewer galleries to Juicebox by following the instructions here.
SimpleViewer Support Team