I received an Aviate Program Guide from United. The document is dated 1 Nov 2019 and it states:
“Candidates who are unsuccessful in the Aviate application process are encouraged to apply to United via the traditional application process. Additional information about this process can be found at the United pilot career website (https://www.united.com/ual/en/us/fly/company/career/pilot.html).”

In Section 6 (Application Process) it says:
“Candidates who apply for the University Path, the Commercial Flight Training Path, or the Experience Path and are unsuccessful will have one additional opportunity to apply to Aviate. Such Candidates must wait for 12 calendar months and have accumulated 500 additional flight hours in order to be eligible to apply a second time and may only apply through the Experience Path or UAX Path. If the Candidate is unsuccessful in his or her second application, he or she will no longer be eligible for Aviate. Notwithstanding the foregoing, Candidates are still eligible to apply for employment with United as a pilot via the traditional path irrespective of any prior application or status with Aviate.
B. The UAX Path Candidates applying for the UAX Path may only apply to Aviate once. Candidates who have applied two or more times to a previous United Career Path Program (CPP) and/or through the traditional path will not be eligible to apply to Aviate (e.g., applying once to a previous CPP and once through the traditional path will be considered applying two times).”