One, plug a keyboard in and press the + key a few times. kodi’s volume indicator should popup to centre of the screen. It’s possible that kodi’s internal sound level ended up turned down some how. Use + and - keys to adjust volume level if this is the case.
Two, check the audio device that you are using, Settings/System/Audio. Try changing it to one that mentions hdmi at the end of it. If it is not already on that one.
The +/- did the trick. Tbh, I didn’t even know Kodi had that key shortcuts. In all the years I’ve been using Kodi on several platforms, I’ve always used CEC.
For some reason the volume was at one third. Putting it back to 100% and volume was back to normal (for me).