My answer to this question on Quora:

How do I resolve the ElementNotInteractableException in Selenium WebDriver?

ElementNotInteractableException is caused when an element is found, but you can not interact with it. For instance, you may not be able to click or send keys.

There could be several reasons for this:

1. The element is not visible / not displayed
2. The element is off screen
3. The element is behind another element
4. Some other action needs performed (by the user) to enable it.

Strategies that may work to make it interactable (depending on the circumstance.)

1. Wait until an element is visible / clickable

   WebDriverWait wait = new WebDriverWait(driver, timeout);
   wait.until(ExpectedConditions.visibilityOf(element));
   wait.until(ExpectedConditions.elementToBeClickable(element));

2. Scroll until the element is within view

   Actions action = new Actions(driver);
   action.moveToElement(element);

3. Use javascript to interact directly with the DOM

   JavascriptExecutor js = (JavascriptExecutor) driver;
   js.executeScript("document.querySelector('locator');
                     element.value = 'whatever';")

4. Perform whatever other action is necessary and possibly wait until after that.

ffmpeg is a command line tool that can convert .flv videos to .mp4 (or another format).

ffmpeg -i video.flv -codec copy video.mp4

Ffmpeg is easy to script, but the number of command line options can be daunting.

handbrake is a GUI application that can also convert .flv to .mp4.

Handbrake is actually a wrapper around ffmpeg that offers sensible defaults but still allows you access to many options.

VLC is an app that can view .flv videos directly.  The VLC Player is free to use.