Hello @Jeremy Wang ,
Welcome to Q&A Forum!
There are many scenarios which can prompt one of these messages. The most frequent cause is that permissions for the user or administrator are configured incorrectly or not configured at all.
You need to ask the administrator or site owners of the site to give you permissions.
For Access Requests, you can refer to the "Set up and manage access requests" for more information.
Thanks,
Echo Du
==========================
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.