SLR viewfinder eyepiece blurred

1; Adjust the diopter of the eyepiece, and you can see clearly by adjusting the small wheel on the side. 2; The lens is too dirty or moldy, and the eyepiece or reflector is oily. 3; The camera or lens is set in manual focus mode, or the lens focus ring is damaged. 4; Camera focusing system is damaged (rare). 5; No batteries.