That's strange, you definitely should be able to select Ask to Activate. ''If you have VLC'' There is an issue in Firefox 49-50 for users with the VLC plugin. Because VLC tells Firefox it can play Flash media, the permissions of the two plugins are linked together. If you have VLC, try setting it to "Ask to Activate". ''Using about:config'' Another way to modify a plugin's default permission is as follows: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful. (2) In the search box above the list, type or paste '''flash''' and pause while the list is filtered (3) Double-click the '''plugin.state.flash''' preference and change the value from 2 (Always Activate) to 1 (Ask to Activate) and click OK. Does it stick?