In my iphone 11 pro ios 15.3.1 true tone disable and sometimes appears. Can you please advise how to fix this problem. Kind Regards

The purpose of the True Tone feature is to ensure that the screen display lighting and overall appearance is balanced with the ambience light. This will reduce strain on the user’s eyes. Often you will find True Tone balancing the display with a Yellow tint and often you will not see any tinting or light adjustment. All of these adjustments depend on the ambient lighting conditions. Is it possible that you may be seeing the differences of True Tone adjustments and then thinking that it sometimes works and sometimes doesn’t?

Axel F.