Some drawing tablets - specifically those with screens - have audio hardware. They don't have speakers (at least not that I am aware of), but some do have a headphone jack so you can listen with headphones.
When you plug in your tablet, the computer may detect that the tablet supports audio, and it can mistakenly assume you want audio to now play through the tablet. And of course because the tablet doesn't have speakers but only a headphone jack the audio is now being sent to your tablet, but you can't hear it.
Here's an example of Windows 11 detecting showing the Huion Kamvas Pro 24 (GT2401) as an audio output.
The solution for this is simple. Just go to your operating system's sound settings and set the audio to go back to where it was going.