Macbook Air 13" 2015 Thunderbolt Port to HDMI troubleshooting

I recently bought my Macbook Air this past May, 2015, and have been very happy with it. Recently, however, I have had trouble with something that has previously (within the life of this macbook air) been functioning properly.

I have a dongle for thunderbolt port connectivity to HDMI. It used to work. Now, it does not work. I have used 2 different adapters of the same function with no successful connection.

To clarify "not work," I mean to say when I plug in the dongle to the thunderbolt port and HDMI cable, and plug the HDMI cable into the TV, the screen does not extend, mirror, or even recognize the connection where it used to turn blue for a moment and connect. What can I do to fix this?