Zip Code is Invalid?
I'm in one zip code and I'm looking at prices of things closer to where I live, but Firefox tells my my home zip code is invalid? USPS delivers mail to my house using that zip code, my home zip code shows up on the national zip code map, how can it be invalid?
Why are we not allowed to shop in a different zip code?
That's not Firefox. Where/how are you getting this error?
You will of course have made sure all the other fields (like State/Province and Country) are filled out (?)
Your system details show that you are using a very old Firefox version; as you are using plugins : would you consider updating to the latest Firefox ESR version ?
If that doesn't make a difference, would you try this please :
Reload the page : Hold down the Shift key and left-click the Reload button or press 'Ctrl + F5' or press 'Ctrl + Shift + R'
Would you try this please :
Clear the Firefox cache :
"Remove the cookies" from websites that cause problems :
https://support.mozilla.org/en-US/kb/delete-cookies-remove-info-websites-stored (scroll down to : "Delete cookies for a single site")
If you use extensions like Adblock Plus, NoScript, Flash Block, Ghostery, then always make sure such extensions do not block (wanted) content.
You could also check your settings here :
If none of the above do the trick, then let's try Firefox in Safe Mode :
If Firefox is not running : Hold down the Shift key when starting Firefox.
If Firefox is running : 3-bar menu => ' ? ' (at the bottom of the dropdown) => 'Restart with Add-ons disabled'. Then OK the restart. A small dialog should appear. Click 'Start in Safe Mode' ( not 'Refresh' !)