He and I talked on the phone every day and even 3 hours two nights ago. Then today he ignored my call. Why the sudden change?

So my ex and I broke up about three months ago. Long distance so mutual. I went no contact for a month. Then reached out and things were going well again as friends. He is currently in my state for work. He was suddenly really responsive and like I said, talked on the phone for hours.

Yet today, he let the call go to voicemail which he never does, then when he called back, he was very short and had to go.

Just confused.

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THANK YOU everyone so far! I appreciate the non-judgmental responses.
He and I talked on the phone every day and even 3 hours two nights ago. Then today he ignored my call. Why the sudden change?
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