I am unable to track on eCAS and I paid with a US credit card online and got a receipt. I have not been able to use that receipt number to log into eCAS. The receipt is filled in with my name (not my sponsor's name), for what it's worth.
Usually when I try to log into eCAS I put in the receipt number and my sponsor's information (because I'm waiting on the sponsorship application for now), but I have tried with my information too. I have also signed up for eCAS tracker.
I also have a client ID (for myself) from a previous student authorization. That doesn't work either but I'm not surprised.
My sponsor (husband) also has a citizenship file number from when he filed for his citizenship card 10 years ago (his parents are Canadian but he was born in the US). That doesn't work either.
I know that many people have been able to log in already, but I'm not TOO worried. I will worry when the date that they are currently processing applications received by passes my date (March 10). OK, I'm worried, but I'm trying not to be! 8)