You are correct , after rereading instructions to comprehend it does call for resetting zero stop. Sometimes a box of rocks and my brain have similarities!!This. Are you sure you do not need to loosen up your zero stop to allow adjustment?
Every time I hear someone say "I can't zero at 100 (or 200)", it has been a zero stop problem. Probably 50 times I have seen it.
Unless something is majorly wrong with the rail, or rings, or mounting holes.
What scope is it you are attempting to use?