I have the same problem, I've travelled to Canada since 2017 staying from weeks to close to 2 months in Montreal with my now fiance (she is there with a work permit). On the day of my flight i was told my eTA was cancelled, checking it says:
"Your application has been cancelled for the following reason(s):
You have misrepresented yourself to obtain an eTA and are not authorised to hold an eTA under the Immigration and Refugee Protection Act"
So I resubmitted for an eTA and got the notice that my case was diverted to the Canadian Mission in Mexico.
I am concerned as to why they would say i misrepresented myself, more concerned that reading in the IRCC page says they could ban me for 5 years.
Does any body know what to expect in time frame to get a response from the Canadian mission?