Some displays are very temperamental with the SNES. My 4k set doesn’t work on Lx2 on 60Hz, yet it works at Lx2 on 50Hz. The only way I can make 60Hz work is with Lx3 with tweaked settings.
What TV do you have?
Also go to output settings and try different modes for 240p. Line x2 is the default setting, though if you have no picture on that then I doubt other modes would work.