Wifi turning off when my iphone is locked

My iPhone 13 pro max starting from last night kept disconnecting from wifi when i locked it. I tired to first turn off and on the wifi and even forget passport but nothing worked. Later, I updated the software to latest 16.2 to solve the issue and still no result. I searched on google and found the reset network method and still after resetting, it still didn’t help and the wifi still keeps getting disconnected about 10 secs after the phone is locked. What should I do at this point?