ETA necessary?

And another question about traveling😅 We have a return flight from New York to Cologne with a stopover of just under 2 hours and a change of airline in Toronto. NYC to Toronto – Air Canada, Toronto to Cologne – Lufthansa I have to apply for ESTA for the trip in general. Now I've read…

Can you be denied an ETA for Canada if you are banned from entering the USA?

My in-laws are coming to Germany from Mexico soon. Unfortunately, my father-in-law is banned from entering the US, so they're flying through Canada, which requires an ETA. My mother-in-law got her ETA right away, but my father-in-law was told he'd have to wait up to 72 hours because he doesn't get it automatically. (The entry…