These are best used for temproary connections. If using them make sure the tab is always down once inserted and if not make sure to fully lift tab, push wire in, and reclose so the WAGO forms a proper connection.
One thing that was difficult to show on the video was the side of the WAGO. It has a guide for how long the stripped portion of the wire should be. To use this put the edge of the insulation against the side of the WAGO and then compare to the end of the black line to check!!!