Try visiting the following Adobe help page in your Edge browser and click the 'Test Flash Player' button to confirm whether Flash Player is currently enabled or disabled. (I'm not sure the instructions on the web page will help though as you seem to be able to display some Flash sites but not others.)
Flash Player issues | Windows 10 | Microsoft Edge - https://helpx.adobe.com/flash-player/kb … -edge.html
There seems to be a lot of Edge vs Adobe Flash Player problems on the internet (try a web search with terms such as "Adobe Flash Player Edge") so you are not alone. However, there does not seem to be sure-fire fix which works for everyone.
Unfortunately, there is no denying that Flash is a dying format and Microsoft seem to be in the process of phasing Flash out.
According to the following article, Microsoft are pushing ahead with their abandonment of Flash in the next version of Windows 10 (Creators Update) which is just around the corner (so anything you try to do to get things working just now may prove to be futile and just a short term fix).
Microsoft's Edge to flush Adobe Flash in Windows 10 Creator’s Update - https://www.theregister.co.uk/2016/12/1 … rs_update/
I realise that you like TiltViewer (and that's great), but, if you want to create a future-proof gallery that works in all browsers (including Edge), I'd recommend moving towards an HTML 5 solution such as Juicebox.
However, I hope the first link above helps.
SimpleViewer Support Team