Android app notifications not working again

Lately I find that receiving notifications for favorited listings is hit and miss. I have a particular local sit that I have in my favorites. I’ve done the sit twice and the homeowners tend to go away every month. I’ve received a couple of notifications but haven’t received any notifications the last two times they listed their sit. Have also noticed this on some international sits that I have favorited - I received no notification. Would like to know from THS why this is happening - thanks.