Error when trying to add products to sponsored AD Group

Hi,

Noticed a problem last week thinking it may be a glitch so left it to try again this week.
Essentially when trying to add products to an existing AD Group within Campaigns the refresh icon (rotating icon!) does not end but get a notification/error message pop-up with the following info:
Request Failure
We were unable to contact our servers. Please check your Internet connection and try again.
Anybody else seeing this?
I really wanted to add some new products but wanted to check if it was an issue localised to my machine/setup or widespread.

Thanks

This issue only occurs for me on Firefox. Adding products via chrome should work as expected.
Not sure why firefox is having issues as I have been using it for Amazon since day 1 and have had no issue.