I had this weird issue where my XReal Beam wasn't charging despite plugging it in for a few hours. One indicator where I knew that could be a problem was because when I plugged in the Beam, the led would flash red for just a second before turning itself off. Even after charging it for a few hours, I couldn't get it to turn on.

After a quick search, I found this Reddit thread that at least got it to start charging. The gist of it is that you need to find a charger that supports PD and then long-press the XReal Beam for it to start charging.

Here's an additional troubleshooting guide for the Beam