You have three options:
- You can complete the declaration that attests you are unable to get your passport and submit it with your PR Card application. However, in Immigroup’s experience, this never works.
- You can become a Canadian citizen. It sounds like you qualify to apply. It will take a long time (a year or more) but it would solve your passport problem and you would no longer need a PR Card.
- You can apply for a Certificate of Identity from Passport Canada. You will likely need to show proof that the Eritrean Embassy has denied your passport application.