Weight of item finds no carriers available issue

[AlanWooler]

Hi all, 

I am using Prestashop 1.7.5.0 and have an issue over weights of items in my cart where if any individual or total weight of an item in a cart is over 100 grams it says there is no carrier available.

I have 3x carriers:

Large Letter
  >=1    < 100 @ £0.79
  >= 100  < 250 @ £1.26
  >= 250  < 500 @ £1.64
  >= 500  < 750 @ £2.22

Small Package
  >= 1  < 2000

Medium Package
  >= 1  < 999

If for example I add 8x Trolley coins (12g each) it says the shipping is £0.79 so it has given the right amount.  If I change it to 9x Trolley Coins, it says the shipping is free and when you checkout the order it says "Unfortunately, there are no carriers available for your delivery address."

I have the same issue with a teddy bear that was specified as 125g and could only be shipped using "Medium Package", it came up with the same error.  If I set the weight of the bear as 99g it works fine.  If I add 2x bears to the cart, the error comes up.  I don't understand as I set the maximum weight for the "Medium Package" to 999g, so why would it error?

I have attached an image of the "Large Letter" carrier.

Thank you very much for any help you can provide me.

This is a shop run by a registered charity in the UK and currently having to manually send invoices through PayPal for this issue as it is causing us a lot of problems.

 

Edited January 27, 2019 by AlanWooler (see edit history)