Could you please send me a private message with the link to the job post you're referring to so I could check? Please keep in mind that if a client changed the visibility of their job post and you've saved it beforehand, you may still be able to see it but not apply.
The job you're referring to was likely posted publicly, and the client updated its visibility to private or invite-only. You will not be able to access this job unless the client invites you to it.
This shows why it's important to have a great profile. Since it looks like you're new, you may want to check out the resources we compiled here and these articles to help you get started on Upwork. Good luck!
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