P2319H, No HDMI signal, Macbook Air 2015

I recently purchased a Dell Monitor P2319H, and after i set it up and plugged it into my MacBook Air through my HDMI port, it worked fine, the display was working well. The next day, I found that the monitor lost connection to my MacBook air after leaving it connected overnight while closing the screen.

After that, the monitor lost signal and it said

"No HDMI signal from your device."

It managed to detect the HDMI on the side of the P2319H, but seemingly not on the thunderbolt at MacBook air. It didn't have a short flicker that would usually happen after i connect my HDMI cable. I've also tried connecting it to my HDMI port on the TV that would usually work, but that didn't work as well.

This leads me to think it was a problem with my MacBook Air. I've tried resetting the SMC and checking for displays in system preferences but nothing has worked so far. Any advice? I can't figure out what is going wrong. Im working on 'High Sierra' version 10.13.6