Error message on "Alternative process for individuals"

Tax Topics
1

When I try to submit an authorization request through Represent a Client, as per CRA’s “Alternative process for individuals” (ie. use NOA info instead of their My Account), I am getting this error which I think is related to the SIN: Field is not valid for this service. (T906)

Anyone encountered this or know how to resolve? (already confirmed that name/SIN is correct)

2

Do you have CRA NOA to confirm the name as CRA has it? and you have their SIN on card or Service Canada letter? (and this is not a first time filer or deceased?)