Yeah i reached the same page as the link you shared. when i enter my application number there and uci number i get this message : incorrect or invalid information. Review and make sure it matches the information submitted on the Use of a Representative [IMM 5476] form or the Authority to Release Personal Information to a Designated Individual [IMM 5475] form. If you can’t create an account, it may be because your client’s application is not in our system yet.I don't know what PR Tracker drop down option you are talking about. I don't see any dropdown. Are you in the correct page?
Is that the link you are using? https://tracker-suivi.apps.cic.gc.ca/en/forgot (and select Principal Applicant or Sponsor)
Also pay attention if there's no empty spaces when copying your UCI and application number (not account number as you said).
I have never used a representative so i dont know what this means. i dont know what to do.