The FCA has been clear: Tax Courts have no power to extend the objection deadline beyond the statutory 90 days plus 1 year, no matter how compelling your reasons. And if you miss your chance to object, the tax assessment stands, no matter how wrong it is. (See ITA s. 152(8) and ETA 299(3).)
See also Topping v. The Queen, (2013 TCC Woods): The fact that "neither [your] accountant nor the CRA provided [you] with sufficient guidance as to how to make an objection" is irrelevant. The deadlines are solid.
See Hanson v. The Queen, (2013 TCC Woods)