I'm subscribed to a few symbols, some of them with thresholds as low as volume >= 10 within 60 seconds, and I still get no alerts.
I'm not getting them in the text alerts window either, even though the bid/ask imbalance alerts show up without any issue. The imbalance voice alerts work as well, so it's not a sound issue.

I also want to mention that there's a spelling mistake in the UI - "Apply this threshold on indicatos's values" instead of indicator's. Could you clarify what that checkbox does, I didn't understand its purpose from the documentation page.
I'm using these accumulation settings for all symbols:

Latest Bookmap build & latest MBO build on WIndows 10
Edit: Thank you for all your responses to the threads I've opened & emails I've sent so far! You've done a great job with Bookmap!