For the first 12 months of using corporate AFR I had the odd issue pop up like you have described. Sometimes even a comma in the address the CRA had on file would cause the software to yell ow at you. Using corporate AFR for the last year has helped me to correct some spelling and other errors that CRA had on file for various addresses. I would perform the initial AFR and if the CRA’s data was incorrect I would log into Represent a Client, do a full address check on all of the accounts (RC, RP, RT, RZ) and overhaul any incorrect data the CRA had on file. Once I did this I would re-AFR the file to make sure everything imported fine.
I think I remember having issues with the Postal Code and can’t remember whether it was actually the postal code causing the flag or anything mis-matched in the address that would trigger the flag on the postal code field. In any event, if I felt the CRA data was actually correct I would just click on the “Use address from T2 Auto-fill” and the yellow diagnostic would go away. I thought this may even have been caused by ghosts left over from the Profile T2 conversion I did a few years back. It could even be that your addresses are using capitals and small letters and the CRA uses capitals only.
As for the “care of” if you want to use ANR Accounting instead of Nelson Selinger then you should log into into Represent a Client and change it there or else you will get this same diagnostic message every year when you use AFR.