Why does he act interested then not?

The compliments and long messages are the least reliable part of his behaviour, because they cost him almost nothing to send on a good day. The gaps tell you more. Look at how long he goes quiet, whether he returns to the same topic, and whether he ever moves the conversation toward a specific time or place. A man who is interested but unsure will often flirt freely and then avoid anything that requires a commitment. That pattern is common and it usually means he likes the attention without yet wanting the logistics. If the gaps are getting longer and his messages are shrinking while the warmth stays the same, he is probably keeping you as a pleasant option rather than working toward something with you.

Replies that work here are light, specific, and easy to answer, without asking him to explain himself. A reply that references something he said earlier shows you were paying attention and gives him an easy thread to pick up. A reply that moves toward a plan, even a loose one, tests whether he is ready to act. What a draft should avoid is anything that reads as a question about the relationship, a reproach about the silence, or a careful effort to seem unbothered. Those drafts put the emotional weight on the reply, which is exactly what makes a man with mixed signals pull back further. Keep the tone easy and let the concrete ask do the work.

If he has gone quiet after a plan or a question, wait a full day before anything else, since many men take a day or two to answer even when they are keen. If there is still nothing, one short follow-up is reasonable, something that restates the question simply without guilt. If he answers with enthusiasm, the pattern may be more about timing than interest. If he answers vaguely or not at all, do not send a second follow-up. Two unanswered attempts is enough information. Stop initiating for a while and see whether he reaches out on his own. If he does not, the mixed signals were the answer, and your attention is better spent on someone who meets you halfway.