We have a hiccup today. Customer address is in the Netherlands and is receiving the Brexit ERROR during checkout.

zen-cart 1.5.6.c

I changed the
Code:
Zone Description:  [135:GBP:Deny]
by removing the : deny (without the spaces) and the error goes away.

Based upon the To Use notes, my original steps were:

Create/Insert Zone Definition:
Zone Name: UK-Brexit
Zone Description: [135:GBP: deny] no spaces
Status: yellow

UK-Brexit Zone Name details:
Country: United Kingdom
Zone: All Zones

Note: Nothing done to the other 3 zone definitions: Idaho, International, USA

Customer in the Netherlands logs into their account, adds items to cart and begins checkout process.
Error message
ERROR: Orders to this destination must be greater than £135
Currency selected: USD
Currency is updated every 3rd day by CRON and was last updated 3/25/2021 @ 10am PDT

I cannot do anything to troubleshoot until after the affected customer places their order, which I expect sometime today.