If your smart video doorbell stops working as soon as it gets dark, there could be several causes. The most common cause has to do with the power supply:
If the doorbell is connected to an 8V bell transformer, instead of the 12V/1A supplied adapter, it may not provide enough power for the doorbell. Especially when it is dark and the doorbell uses more power because of turning on infrared lights or night vision functions.
The smart video doorbell has a specific power supply requirement. In this case, it is recommended that the doorbell transformer provide a voltage of 12V and a minimum current of 1 amp.
To solve this problem, you could install a new bell transformer that meets the required specifications of the smart video doorbell. A 12V bell transformer with a current rating of at least 1 amp should provide the doorbell with sufficient power, even in the dark.
However, it is also possible that there are other factors contributing to the problem, such as a poor Wi-Fi connection.