The community owner might require new members to obtain manual approval. When manual approval for a community is set, the owner reviews each request and makes a decision based on their criteria. If you're a community owner and want to set up manual approval, read Set up your community join requests.
Once you send a request to join a community, your request can be accepted or not. To check the status of your request, go to the community screen.
If the community owner approves your request to join, you get access to the community immediately.