The PBS Passport membership is a benefit provided solely by PBS streaming websites and apps.
You may notice both PBS and other providers offer some - but not all - of the same programs for online streaming. This is because PBS and other providers are distributors of content and must purchase streaming rights for certain programs, and sometimes both PBS and other providers purchase streaming rights for the same program. Though the content may be the same, the sites and services are separate.
For example, if you have purchased a subscription to Amazon Prime Video or are trying a free trial, this can only be used at Amazon's site and apps. You will have made an account specifically for Amazon. Both this account and service cannot be used at PBS. Likewise, a PBS account and Passport can not be used at Amazon's site or apps. Other sites separate from PBS or a member station will not recognize your Passport benefit.
If you are trying to watch Passport videos, you must sign in at the PBS Home Page or another supported PBS website or PBS Video app.