Apartment buzzer integration not working

Once I got a new iPhone 13 pro it seems to have stopped working with my apartment’s buzzer system. Normally all I have to do is answer a call and dial 9 to buzz someone in, but now when I press 9 nothing happens, and visitors and deliveries are stranded outside.

The apartment manager talked to the buzzer maintenance guy who said that everything is fine on their end, so it must be an issue with my phone.

I wonder if the phone automatically mutes the number/key noises during a call so it isn’t being picked up by the call box? And if there’s any way to change the settings?

I’ve seen other posts where people have similar issues but I haven’t seen any solid answers.