Hmm, usually that button comes to life after a delay of 1-2 seconds. This is for security reasons that I think are related to avoiding bots downloading things automatically, or something like that. If you want to test whether the OK button gets enabled if you remove the delay, here's how you could try that: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button accepting the risk. (2) In the search box in the page, type or paste '''dialog''' and pause while the list is filtered (3) Double-click the '''security.dialog_enable_delay''' preference to display an editing field, and change the value to '''0''' then press Enter or click the blue check mark button to save the change. (To restore the default value of 1000 later, you can use the arrow button at the right end of the row.) More info on about:config: [[Configuration Editor for Firefox]].