I am not getting voltage on 15v and 3.3v pin of Daily Bms uart port.

I am using a external data logger which works on 15v of daily bms. And send commands using uart and save data into sd card. Everything is working correctly but few of my bms suddenly stop working I checked the voltage pin of uart. The output is 0 on both pin 15v and 3.3v. Uart is not working anymore but bms is taking charge and discharge.

Hate to say it but it's likely the MCU has completely failed and the other IC is still managing the cells based on it's last programmed configuration.

I have worked with GigaDevice STM32 clones in the past and have had them just randomly fail like this, not exactly a quality part.

You might be able to repair it by replacing the MCU which I am currently in the process of doing myself, see:

Confirmed that the 2nd device (SH367309) on the BMS can run standalone once configured, your MCU has died. I found and have attached the English datasheet for it if you want to try to interface to it directly via I2C.