... when viewed in firefox or google chrome the gallery ends up just showing the thumbnails only. I'm guessing the browser is triggering the simpleviewer gallery to show the mobile app mode.
That is correct. The Mobile Player within SimpleViewer was designed to display the gallery on mobile devices so the thumbnails and main images are displayed on separate pages to give the main images as much room as possible on small screen devices. At least the Mobile Player within SimpleViewer allows your gallery images to be displayed and viewed if Adobe Flash Player is not installed and enabled in the browser. (Prior to the Mobile Player being introduced in v2.1.0, SimpleViewer just displayed a "Flash Player required." message instead of any images at all if Adobe Flash Player was not available.)
Many browsers are now blocking Flash content by default (here are links regarding Edge, Chrome and Firefox) and this can trigger the gallery to be displayed by the Mobile Player rather than the Flash Player.
Unfortunately, there is nothing that can be done from within a SimpleViewer gallery to prevent this. Please see this SimpleViewer blog entry for more information (and details of our alternative HTML 5 image viewer, Juicebox). Also, this blog entry explains why we created Juicebox in the first place.
You can check to see if Adobe Flash Player is active in your browser by visiting this Adobe help page.
If you see the problem in Chrome, then please try the following steps.
(1) Open Chrome
(2) Click the 'Options' button (the three vertical dots near the top right)
(3) Select 'Settings'
(4) Scroll down to the very bottom
(5) Click the 'Show advanced settings...' link
(6) Scroll down to the 'Privacy' section
(7) Click the 'Content settings...' button
(8) Scroll down to the 'Flash' section
(9) Select 'Allow sites to run Flash'
(10) Click the 'Done' button at the bottom right
Please see this support page for details on how to 'Always Activate' Flash content in Firefox.
Unfortunately, there is nothing that you can do to ensure that visitors to your web site have Adobe Flash Player installed and enabled in their own browsers.
Additionally, Flickr now prevent Flash applications from displaying images on their servers (please see this forum post for details) and Adobe have recently announced that Flash will reach its end of life in 2020.
Here's a short quote from this Adobe blog entry.
Specifically, we will stop updating and distributing the Flash Player at the end of 2020 and encourage content creators to migrate any existing Flash content to these new open formats.
With the demise of Flash imminent, I would recommend switching your SimpleViewer galleries to an HTML 5 equivalent, such as Juicebox, which will not be affected by any of the problems currently affecting Flash content.
As a SimpleViewer-Pro user, you are entitled to a 30% discount off the cost of Juicebox-Pro. Details are in our blog entry here.
If you were to purchase Juicebox-Pro, you can convert a SimpleViewer gallery to Juicebox by following the Converting a SimpleViewer Gallery instructions.
I hope this helps to clarify things.
SimpleViewer Support Team