The bot got removed from my meeting
Host removed it, platform kicked it for inactivity, network drop.
If Meetbook's recording stops partway through, check the meeting page — a banner explains what happened at the point recording stopped.

The host (or another participant with permission) removed it
Anyone able to remove participants can remove the notetaker like any other participant. If this happens regularly in a recurring meeting, tell whoever's removing it that Meetbook is there to record — often it's simply unfamiliar and gets removed by reflex the first time.
The platform removed it for inactivity
Some platforms automatically drop participants that neither speak nor show video activity after a long period — since the notetaker is a silent, non-video participant, very long or very quiet meetings can occasionally trigger this. The recording made up to that point is still saved.
Network drop
A connectivity issue on Meetbook's side occasionally disconnects the bot mid-meeting. This is uncommon; if it happens, everything captured up to the disconnect is still saved as a normal (shorter) recording.
What you get either way
Whatever was captured before the bot left is saved and transcribed normally — you don't lose the whole meeting, just the part after it was removed. If the resulting recording seems unexpectedly short, see My recording is much shorter than the meeting.