Back when I ordered a Quest 2 I had to use a space somewhere in my zip code for it to work. Like "123 45" or "12 345". Do not remember the variant that worked!

Well a postal code is an invalid zip code, so not sure what you are expecting. If you select Canada in the "ship to" field it will work.

I had selected Canada but I will reselect it. Tried it a few more times and when I enter in my postal code into the field labelled “postal code” it tells me it is an invalid zip code.

Once I switched from Safari on iOS to Chrome on MacOS it worked.