The problem is simple.
For some reason, you are listing on eBay.com instead of eBay.ca
Some of your listings do not show "ship to Canada". They show "ship to USA" only. For example: 281437209502
All you need to do is revise your listings and include shipping to Canada with a shipping method and shipping charge to Canada.
You could avoid that problem by listing on eBay.ca where eBay offers you Canada Post options (not available on eBay.com)