Hi Bouchay
I had similar problems with my MiaoMiao. It stopped working after a sensor change. Likes your it would not connect to the new sensor. The sensor was working well. I emailed the company. They eventually responded.
Please try the following steps:
1: Reset miaomiao holding down the hole at least 60 seconds at the back of miaomiao to reset it. Then, try to charge it for 2-3 hours to see if the green light is on or not.
2: First ensure that the MiaoMiao, is placed on top of the sensor in accordance with the instructions; replace it again no gap
3: please turn off your app and then restart it.
4: please turn off and on your bluetooth.
5: maybe you need to use another app to try.
None of these actions helped. When I contacted them again the agreed to replace the MiaoMiao. I had to return the faulty one to an address in the UK and send them the tracking number. As yet I have not received the replacement.
Hope this is helpfull