Which is your OS? How about checking them with Acrobat Reader?
I am working under OpenBSD and context TeXLive 2017 pre-release. Acrobat Reader is not avalaible. Btw, I had the same issue as you under Linux : Evince could'nt display slides with Steps macros, while mupdf displays content without steps. The new mkiv Rawsteps nearly works for me with mupdf : both steps are displayed on the same slide, which is not what is intended, but at least contents are duplicated. If steps are only working with AcroRead, this means that steps may rather rely on a workaround and it might be considered a kind of bug. Unfortunately my programming skills are none, so I migt be exagerating. Anyway it would be really great to have something working with poppler and mupdf engines. Could the \pause macro from beamer be a starting point or is this too LaTeX dependant?