Problems in "Cart" page – coupons, updating quantities, proceed to checkout

I’m having three problems with cart page:

1) Adding a coupon code does not work in the cart. When the code is entered, the screen refreshes, but the coupon discount is not applied. Adding the coupon does work at checkout.

2) Changing the quantity of an item already in the cart and clicking update does not change the quantity — the screen refreshes and the item quantity reverts to whatever was passed from the product page.

3) Clicking “Proceed to Checkout” does nothing.

The link to my shop is: https://www.on30guy.com/shop or https://on30guy.gerenm.net/shop

Problem #3 seems to have happened after updating to WP 3.9.
Problem #2 has never worked correctly.
Problem #1 is new, as I’ve just tried implementing coupons today.

I have tested in the latest versions of Chrome and Internet Explorer. I have tried disabling all other plugins.

System Report:

### Environment ###

Home URL: https://www.on30guy.com
Site URL: https://on30guy.gerenm.net
WC Version: 2.1.7
WC Database Version: 2.1.7
WP Version: 3.9
WP Multisite Enabled: No
Web Server Info: Apache
PHP Version: 5.3.28
MySQL Version: 5.5.32
WP Memory Limit: 64 MB
WP Debug Mode: No
WP Language: Default
WP Max Upload Size: 20 MB
PHP Post Max Size: 20 MB
PHP Time Limit: 120
PHP Max Input Vars: 1000
SUHOSIN Installed: No
WC Logging: Log directory is writable.
Default Timezone: Default timezone is UTC
fsockopen/cURL: Your server has fsockopen and cURL enabled.
SOAP Client: Your server has the SOAP Client class enabled.
WP Remote Post: wp_remote_post() was successful – PayPal IPN is working.

### Locale ###

decimal_point: .
thousands_sep:
mon_decimal_point:
mon_thousands_sep:

### Plugins ###

Installed Plugins: Add drafts by Dan Stefancu version 1.0
Admin Show Sticky by Matt Martz version 1.0
Akismet by Automattic version 3.0.0
Contact Form 7 by Takayuki Miyoshi version 3.8
WordPress Duplicate Content Cure by Badi Jones version 1.0
Easy Lightbox by Mesut Savvas version 1.0
YouTube Advanced by Embed Plus by EmbedPlus Team version 4.6
Events Manager by Marcus Sykes version 5.5.2
EzStatic by Owen Winkler version 3.1.1
Health Check by The www.ads-software.com community version 0.2.1
INK – Own your content by Stephane Caron version 1.0.7
Jetpack by WordPress.com by Automattic version 2.9.3
Max Image Size Control by Hiroaki Miyashita version 0.2.3
Ninja Pages
Categories
and Tags by The WP Ninjas version 1.3.2
Organize Series by Darren Ethier version 2.4.6
Peter’s Login Redirect by Peter Keung version 2.7.2
Q & A Plus by momnt version 1.1.1
Regenerate Thumbnails by Viper007Bond version 2.2.4
Resize At Upload Plus by Daniel Mores
A. Huizinga version 1.3
Shutter Reloaded by Andrew Ozz version 2.5
SI CAPTCHA Anti-Spam by Mike Challis version 2.7.7.3
User Role Editor by Vladimir Garagulya version 4.11
WooCommerce by WooThemes version 2.1.7
WordPress Database Backup by Austin Matzko version 2.2.4
wp-Table by Alex Rabe version 1.52

### Settings ###

Force SSL: No

### WC Pages ###

Shop Base: #2800 – /shop/
Cart: #2801 – /shop/cart/
Checkout: #2802 – /shop/checkout/
My Account: #2803 – /shop/my-account/

### WC Taxonomies ###

Order Statuses: cancelled (cancelled)
completed (completed)
failed (failed)
on-hold (on-hold)
pending (pending)
processing (processing)
refunded (refunded)

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

### Theme ###

Theme Name: Twenty Fourteen
Theme Version: 1.0
Author URL: https://www.ads-software.com/

### Templates ###

Template Overrides: No overrides present in theme.

https://www.ads-software.com/plugins/woocommerce/