Following filter works great in Windows...even online its working great.
In android mobile it says "NO TASKS"
!@MyLabel & (priority 1, priority 2, priority 3)
Thank you for your report, we'll look into it.
For now, please use this query instead:
p1 & !@MyLabel, p2 & !@MyLabel, p3 & !@MyLabel
This will also work correctly on other platforms as the one you've posted is wrong even on the web and has shown me tasks with priority 4.