"Manage Orders" in Wordpress Admin leads to a dead link

I am currently busy testing in the Sandbox environment with PayPal chained payments.

I have just been able to purchase a product in one of my sub-sites and all went well via Sandbox.

I then afterwards went into Wordpress Admin of the sub-site to manage the order only to find that by clicking on "Manage Orders" leads to a dead link ie edit.php?post_type=product&page=marketpress-orders

However when I navigate to the main site the "Manage Order" links does work.

This is the message that I receive in:

Chrome:

This webpage is not available
The webpage at http://fraga.co.za/wp-admin/edit.php?post_type=product&page=marketpress-orders might be temporarily down or it may have moved permanently to a new web address.
Error 330 (net::ERR_CONTENT_DECODING_FAILED): Unknown error.

and in

Firefox:

The page you are trying to view cannot be shown because it uses an invalid or unsupported form of compression.
Please contact the website owners to inform them of this problem.

Kindly assist.