Screenshot takes 2 tries

I added a "get screenshot" function to my game. When I'm previewing it in Mozilla and click the button to get the screenshot, it opens a new window that is completely black. After that when I click on the screenshot button it lets me open it in Paint. Am I missing something here? Here's my code:

On tap "Text2" System take snapshot of canvas

Function: call CanvasSnapshot()

Browser: invoke download of CanvasSnapshot with filename "Answers"

https://www.scirra.com/manual/126/system-expressions

[quote:3rssxxyz]CanvasSnapshot

Contains the resulting image from a Snapshot canvas action after On canvas snapshot has run. (Note this expression is not available immediately after the Snapshot canvas action - you can only use it after On canvas snapshot triggers.) The expression returns a data URI of the image file. This can be loaded in to a Sprite or Tiled Background object via Load image from URL, sent to a server or stored locally, or opened with the Browser object in a new tab to save to disk.