Field test mode not working

I want to display my cellular signal readout in dBm as I have in the past. I dial *3001#12345#* to initiate field test mode, then hold down power until the slider appears then hold home to go back to home screen. When I get back to the home screen my signal is still displayed by the bubbles. Am I missing something here? On an iPhone 7 Plus running 10.3.3 on AT&T.