Ring Doorbell 3 plus not detecting people after 1 month of using

I just bought my Ring doorbell3 plus last month and started using it. Initially it works fine, whenever someone passed by, there were notification and events recorded in the Ring doorbell. However, starting from last week, the doorbell has not been detecting any motion movement. like when the delivery person approached my door for delivery or my neighbour passed by (I lived in an apartment, there is a corridor outside my door). I was in the house and I knew such motions but the Ring wasn't detecting anything at all! I am sure the placement of the ring is correct, not too high or too low. Because it was detecting in the first month. I have trued to reset the ring to factory setting, change the configuration like Maximise motion sensitivity level, fully charge the battery, Motion Frequency as Frequent and people only mode. After a lot of trial and error but it still failed to serve its purpose. I am so disappointed. Also the Singapore customer service hotline number in the Ring website are invalid. Both numbers are invalid. I really hope the problem is solved as this is a security concern now.