Why is my mode indicator not working? Minolta Maxxum 300si

On the 300si these are essentially so stripped down they are fully automatic SLRs of the 90's. You cannot change it into a manual mode, but you can press the mode button and switch the predefined shooting scenes. When you have not selected one, the camera is making all of the decisions.

Enabling one of the shooting modes (partially) overrides the full auto nature of the 300si, but not completely. There's sadly no way to add a manual mode to these as they were severely cost-reduced to appeal to beginners who didn't want to buy a proper film SLR back in the day. However, Minolta is not alone; Canon and Nikon have some too. The market responded by saying we do not want these. I'd sooner deal with the aperture gear problems on the Maxxum 7 over a 300si, or even buy a Maxxum 5.