Adobe Flash Player Issue with latest FF Version

Dear All,

since yesterday I experience some strange issues with Adobe Flash Player V25 and FF53. When I want to load a site which requires flash interaction, this site tolds me: You dont have flash player installed, Please go to Adobe and download flash player

But, I have installed and activated the latest Flash Player Version V25. On the following adobe flash player checking site (pleaae excuse the german language) https://helpx.adobe.com/de/flash-player.html

Hilfe zu Flash Player I clicked on the check now button but nothing happends. Moreover I cannot see the aninmation in point five. However, this site from Adobe tells me I do have it installed Adobe - Flash Player

I did a lot of steps from the flash player support site (Häufige Probleme ) and from the firefox support site (Fehlerbehebung bei Plugins wie Flash oder Java, um verbreitete Probleme mit Firefox zu lösen | Hilfe zu Firefox ) again please excuse the german language for the sites. It should be just an example what steps I already did to solve the problem.

But in the end I am not able to run the site which requires flash. I have an older laptop, also with FP V25 and FF53 installed and here it works.... But on my laptop it does not work. Neither with FF nor with IE oder Chrome....Always the same message: You dont have installed Flash Player.

What else can I do?

Bestregards

Pat