EOS 300 SLR - Won't power up or turn on in any way

Have not used my EOS 300 SLR Film camera in a while ,. Would not switch on by rotating function dial from the red ‘ L ‘ off position to any setting . Bought new batteries , replaced in camera . Still wouldn't turn on or power up in any way. I have checked battery contacts and they are clean and in good condition with spring in them when gently pressed.

Can someone help please