Some users cannot use 'Proceed to Checkout' button

Hi,
The issue I am currently having is that 2 users cannot use the ‘Proceed to Checkout’ button on my cart page. However when I recreate this on the same browser and user it works fine for me, as well as a few other users they have not experienced this issue and can proceed to the checkout.

The site is for a large restaurant company who we print for 60 of there sites and we are getting them online so its a must this has to be fixed ASAP otherwise I am a DEAD MAN, I have just updated all of my plugins and WordPress but the issue was there just before I done the updates so its not a issue of new updates screwing up the files. I will post the system status of my woocommerce below. Any other info you need let me know.

Many THanks Luke

### WordPress Environment ###

Home URL: http://eagleprinters.co.uk/onlineprint
Site URL: http://eagleprinters.co.uk/onlineprint
WC Version: 2.5.2
Log Directory Writable: ✔ /home/eaglepri/public_html/onlineprint/wp-content/uploads/wc-logs/
WP Version: 4.4.1
WP Multisite: –
WP Memory Limit: 2 GB
WP Debug Mode: –
Language: en_US

### Server Environment ###

Server Info: Apache/2.4.16 (Unix) OpenSSL/1.0.1e-fips mod_bwlimited/1.4
PHP Version: 5.5.28
PHP Post Max Size: 32 MB
PHP Time Limit: 360
PHP Max Input Vars: 1000
SUHOSIN Installed: –
MySQL Version: 5.5.47
Max Upload Size: 32 MB
Default Timezone is UTC: ✔
fsockopen/cURL: ✔
SoapClient: ✔
DOMDocument: ✔
GZip: ✔
Multibyte String: ✔
Remote Post: ✔
Remote Get: ✔

### Database ###

WC Database Version: 2.5.2
:
woocommerce_sessions: ✔
woocommerce_api_keys: ✔
woocommerce_attribute_taxonomies: ✔
woocommerce_termmeta: ✔
woocommerce_downloadable_product_permissions: ✔
woocommerce_order_items: ✔
woocommerce_order_itemmeta: ✔
woocommerce_tax_rates: ✔
woocommerce_tax_rate_locations: ✔

### Active Plugins (19) ###

Adminimize: by Frank Bültge – 1.9.2
Admin Columns: by AdminColumns.com – 2.4.9
Contact Form 7: by Takayuki Miyoshi – 4.3.1
Envato WordPress Toolkit: by Envato – 1.7.3
Salient Visual Composer: by Michael M – WPBakery.com | Modified by ThemeNectar – 4.3.5
VarkTech Min and Max Purchase for WooCommerce: by Vark – 1.07.91
Ninja Forms: by The WP Ninjas – 2.9.33
User Role Editor: by Vladimir Garagulya – 4.23
Woocommerce Advanced Free Shipping: by Jeroen Sormani – 1.0.8
WooCommerce Catalog Visibility Options: by Lucas Stark – 2.6.1 – 2.7.0 is available
WooCommerce Checkout Field Editor: by WooThemes / Mike Jolley / Patrick Garman – 1.4.3 – 1.4.10 is available
WooCommerce Customizer: by SkyVerge – 2.2.0
WooCommerce Ninja Forms Product Add-Ons: by WooThemes – 1.1.0 – 1.1.4 is available
Woocommerce Products Designer: by ORION – 3.4
WooCommerce: by WooThemes – 2.5.2
WooThemes Helper: by WooThemes – 1.5.9
WP Add Custom CSS: by Daniele De Santis – 0.9.7
Wordpress File Upload: by Nickolas Bossinas – 3.7.1
WP User Avatar: by flippercode – 2.0.4

### Settings ###

Force SSL: –
Currency: GBP (£)
Currency Position: left
Thousand Separator: ,
Decimal Separator: .
Number of Decimals: 2

### API ###

API Enabled: ✔
API Version: 3.1.0

### WC Pages ###

Shop Base: #10 – /shop/
Cart: #11 – /cart/
Checkout: #12 – /checkout/
My Account: #13 – /

### Taxonomies ###

Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

### Theme ###

Name:
Version: – 0 is available
Author URL:
Child Theme: ✕ – If you’re modifying WooCommerce on a parent theme you didn’t build personally
then we recommend using a child theme. See: How to create a child theme

WooCommerce Support: ✔

### Templates ###

Overrides: birdpress/woocommerce/cart/cart-shipping.php
birdpress/woocommerce/cart/cart-totals.php
birdpress/woocommerce/cart/cart.php
birdpress/woocommerce/cart/shipping-calculator.php
birdpress/woocommerce/content-product.php
birdpress/woocommerce/content-single-product.php
birdpress/woocommerce/single-product/product-image.php
birdpress/woocommerce/single-product/tabs/description.php
birdpress/woocommerce/single-product/tabs/tabs.php

https://ww.wp.xz.cn/plugins/woocommerce/