The warning sign is "you need flash player to complete this activity"
I have searched / followed all the instructions / tested the flash player where it shows tree and clouds - all works fine
however when I go on the above website mathletics.com it still doesn't work.
Any idea ???
If Flash is working elsewhere, but not on this site, the issue is most likely going to be with the site not conforming to Edge's click-to-play implementation. Edge, like most modern browsers, disables Flash by default. On Edge, users MUST enable Flash on a per-site basis. There is no 'always allow for all domains' option. Usually, there is a 'get Flash Player' button/link or similar. Based on the screenshots you posted, I can't tell if this button/link is present on the page (or in the hidden warning message). When the user clicks the button/link, Edge intercepts the request and displays the 'Allow Flash' dialog window. See Troubleshooting Flash Player on Microsoft Edge (and Extending User Control of Flash with Click-to-Run - Microsoft Edge Dev BlogMicrosoft Edge Dev Blog) for more information. Unfortunately, Mathletics requires a subscription service to get to the page you are at, thus, I'm not able to access the page to troubleshoot further..
Essentially this is an issue with the content, not Flash Player. I recommend contacting Mathletics for assistance. The second link I posted (Microsoft blog post) contains information on reporting the to Microsoft.