Few hobbies are less productive than trying to decode an uninterested person's punctuation. Sometimes a conversation changes pace for ordinary reasons. Sometimes the interest simply isn't mutual.
Look at the overall pattern
One late reply tells you very little. Repeated cancellations without a suggested alternative, persistent one-sided effort or clear statements of disinterest tell you more. Avoid building theories out of one odd message.
Ask once and accept the response
If you're confused, a calm question is better than a long accusation. 'I'd enjoy seeing you again. Would you like that?' is enough. If the answer doesn't move things forward, give it space and return to your own life.

METHOD✶
Make it work in real life
Take a situation you're overthinking and separate observations from assumptions. Make one reasonable decision based on what you actually know.
Everyone brings different experiences and expectations to dating. Pay attention to the person rather than relying on a single rule, and don't assume somebody else's interest, availability or intentions. A good outcome is clarity and a respectful conversation, even when romance does not follow.
THE GOLDEN
RULE.
Attraction isn't a switch you can flick in another person. Work on being somebody comfortable, engaging and respectful to spend time with — and give others the freedom to choose for themselves.
YOURS, MONTGOMERY.