According to this article about the River City Romance Writers Chapter of Romance Writers of America: "PRO means you have a completed manuscript and sent it to at least one editor/agent/publisher and it has been rejected." If you have completed and submitted a manuscript, and it is accepted, you presumably remain an amateur.
Assuming this was a typo I looked up the definition, but no, it was quite correct. "PRO was created to serve RWA members who are pursuing publication, but are still waiting for "the call" from a publisher." As opposed to PAN (Published Authors Network).
But what on earth is PRO meant to stand for? Please Renew with our Organization? Politely Remain Outside?