PayPal IPN data not received and Post-Payment Redirect

I have a client that is having multiple issues in regards to her Drupal Commerce/Commerce Paypal setup and I was hoping someone could help shed some light on what the solution may be.

Site: https://www.judithm.com

Description of Problem: There are two issues that we are encountering and they may be related.

1. When completing a payment with PayPal, the order status is never updated and no payment information is sent back to Drupal Commerce for that order. Subsequently, no rules are fired so no emails are sent. However, the payments are showing correctly in PayPal, but minus the IPN history
2. When clicking the "Return to Judithm Site" button after submitting the PayPal payment, it sends me back to the page which originally performs the redirection to paypal.

Additional Information: This is a recent problem, and has only started occurring over the weekend. Prior to this, Paypal payments were working correctly.

When placing a test order, the following form values were created on the page that redirects to PayPal

    <form action="https://www.paypal.com/cgi-bin/webscr" method="post" id="commerce-paypal-wps-redirect-form" accept-charset="UTF-8"><div><input type="hidden" name="cmd" value="_cart" />
<div class="checkout-help">Please wait while you are redirected to the payment server. If nothing happens within 10 seconds, please click on the button below.</div><input type="hidden" name="upload" value="1" />
<input type="hidden" name="business" value="orders@judithm.com" />
<input type="hidden" name="notify_url" value="https://www.judithm.com/commerce_paypal/ipn/paypal_wps%7Ccommerce_payment_paypal_wps" />
<input type="hidden" name="charset" value="utf-8" />
<input type="hidden" name="no_note" value="1" />
<input type="hidden" name="no_shipping" value="1" />
<input type="hidden" name="cancel_return" value="https://www.judithm.com/checkout/5256/payment/back/OanOXvwoh9ZxdzAkQ3KRkSMzxUEwrG67MZ7FWDKNgOY" />
<input type="hidden" name="return" value="https://www.judithm.com/checkout/5256/payment/return/OanOXvwoh9ZxdzAkQ3KRkSMzxUEwrG67MZ7FWDKNgOY" />
<input type="hidden" name="rm" value="2" />
<input type="hidden" name="paymentaction" value="sale" />
<input type="hidden" name="currency_code" value="USD" />
<input type="hidden" name="lc" value="US" />
<input type="hidden" name="invoice" value="5256-1359399365" />
<input type="hidden" name="amount_1" value="0.7" />
<input type="hidden" name="item_name_1" value="Order 5256 at Judith M Millinery Supply House" />
<input type="hidden" name="on0_1" value="Product count" />
<input type="hidden" name="os0_1" value="1" />
<input type="submit" id="edit-submit" name="op" value="Proceed to PayPal" class="form-submit" /><input type="hidden" name="form_build_id" value="form-9IJaUfj770RiBUbWwJjzd8fQ20_NgJ9bQjO4IywYfnw" />
<input type="hidden" name="form_token" value="B0v5J36XaAkCyXLTgmv46hc3MNF2uz5sQHKVt6ZI50I" />
<input type="hidden" name="form_id" value="commerce_checkout_form_payment" />
</div>

PayPal Settings:
We have the auto-redirect setting turned off.
IPN notifications are turned off, though I have tried with them both on and off with no difference in results.
The Order E-Mail is the same as the one in PayPal.

Testing Information:
I have tried a variety of methods to test this to determine the issue. I've checked the Drupal logs to see if there were any errors in there, and there were none. I am able to access the IPN url directly in my browser and there isn't any indication that it is returning a 404.
I've checked the server logs and am not seeing anything that stands out as incorrect, but I'm not seeing any post data from PayPal in the access_log to the notify_url in the order
I have tried the solutions listed in #1055390: Invalid notify_url, but still nothing.

Does anyone have any thoughts as to what the problem could be? Thanks for your help!