That's weird coz you should be able to access your ECAS by now. Please double-check that you're entering all the information correctly.
Visit this link (bookmark it):
https://services3.cic.gc.ca/ecas/security.do
Select the option
I have read, understood and agree with the above Terms and Conditions (checkmark) >> Continue
Identification Type: Application number/Case number
Identification number: Type your application number from the AoR email that you've received. Double-check and make sure that there are no spaces before or after.
Family Name: (Your last name)
Your DoB:
Place of Birth: (Your home country)
If you're doing everything right and still not able to log in, then you gotta call IRCC call centre tomorrow morning and figure out what's happening. I hope you get a solution to your issue soon.
Good luck!
Kal