It used to be that on my Nikon D5200 camera holding down the shoot button halfway the viewfinder would show green dots and it would focus nicely.
Now after resetting the camera settings, replacing the battery, trying different focus modes etc. (Manual and automatic) I can never get those green dots to show up.
Instead, only a single red dot is shown. Could the issue be my lense, phtoosensor or the camera's settings? I have very little knowledge of DSLRs.