What does it mean when someone says, "We're just not on the same page"?

A guy I was seeing told me via text that we "just weren't on the same page" when I told him I couldn't do the casual thing. He said he was never looking for casual but everything was past tense and that was sort of that.

We were trying to make plans but our schedules clashed for pretty much 2 weeks. I gave him notice of my business trip well in advance but he 'forgot' until pretty much the last minute to tell me he was out of town the weekend prior to my trip. I guess I felt if this were an honest mistake the phone would be better and text was shady.

Left wondering if things were just lost in translation or an obvious blow off.... 5 dates with sleep overs so kinda sucky way to fizzle out. Is this soome sort of, 'mistakes were made' neutral way to cut and run?
What does it mean when someone says, "We're just not on the same page"?
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