What does it mean that the leader asks for leave and doesn't reply?

There are three possible reasons for this.

1, busy or forgotten: the leader may be too busy to notice your request for leave or forget to reply. This doesn't necessarily mean that they don't agree to your leaving.

2. Need further consideration: The leader may need to consider your leave request, such as evaluating your work progress, the needs of the team and the company's policies. They may need time to make a decision, so they haven't replied yet.

3. Do not agree to ask for leave: Although it is unlikely, the leader may not agree with you to ask for leave. They may think that your departure will have a negative impact on your work, or it is not in line with the company's policy.