Shipping cost cannot be calculated. Please enter a valid Postal Code. this is a pain

[fish-on6]

this comes up now on all my listings " Shipping cost cannot be calculated. Please enter a valid Postal Code." my mail is flooding with buyers asking for specific shipping quotes... I have listings set up as the actual price..... earlier today it was fine it displayed the calculated cost of shipping and all was well. now all my listings say calculate and it give me the cant calculate ordeal. It is very time consuming and along with all the upset buyers trying to get answers im afraid they will jeopardize my rating. I am new to this but this just doesn't make sense as it should calculate and save me the headache... am I overlooking something? any ideas? 

[fish-on6]

I shouldn't have to write up an invoice every single time I sell an item. there has got to be a solution....

[aubreyclay56]

i looked at your site and seem to get different prices on each of your lots some are 10.00 some are 14.00,ive heard people say on here that the shipping calculator is not always acurate,im in canada by the way,and that seems like cheap shipping,i never use that shipping calculater to list my items,although ive tried to use the shipping calculator on us sellers sites and it mostly says invalid postal code contact seller,but just as long as you know ebay charges final value fees on shipping ,so the one item that says 14.31 to ship you have listed will cost you 1.42 in ebay fees plus whatever paypal charges thats one reason i dont use it