What am I drilling into here?

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This is a continuation of a problem I had yesterday, but once again, I'm having trouble mounting a padeye for a sunshade, and it feels like no matter where I drill into this wall, I hit something extremely hard (can't drill further). I'm making sure I'm using a stud finder on the inside of the wall, then measuring from the window, and then grabbing the same distance from the outside. Currently using a hammer drill with a masonry bit, and I'm not too sure what I'm doing wrong. Any tips can hel...