Tiling over vinyl flooring is often done here in SW Florida. The sub surface must be solid, not a problem here as all are on concrete or terrazzo. Cut away any flooring that is lifting, and feather edge with leveling compound. After that follow the instructions on the thin set mortar bag. Use an additive to promote adhesion. Do not attempt this with mastic. Good Luck, I'm off to complete just such a job this morning.