Booting on external SSD only shows black screen

For the past several months, I've been booting off of a Samsung T5 external SSD for school projects. As the computer turns on, I hold down the Option key, which allows me to select the drive I'd like to boot off of. It's worked very well for my needs.

Now, after I select the external drive to boot from, it just goes to a black screen that hangs indefinitely. I don't know what changed. Any advice appreciated, thank you.