I want to attach a new shower system to my shower wall. It includes a mounting plate with three 4mm screw holes. I have successfully drilled the holes in the tile using a diamond-tipped drill bit. The carbide-tipped masonry drill bit recommended in the installation instructions didn't work, because the tiles are porcelain and therefore too hard.
Now that I have the holes drilled, I am having trouble with the supplied masonry anchors (pictured below). When I try to use them to fix the mounting plate to the wall, they fail to cut through the tile and instead the threads get flattened.
I'd like a recommendation for how to mount the mounting plate securely to these porcelain tiles, ideally using the 4mm holes I have already drilled (as they match the screw holes in the mounting plate).

Supplied masonry anchor