Unable to download Firefox extension.

Unable to download Firefox extension.

Hi, I am just trying out Zoho Vault & I am not able to download the Firefox extension, I get the message " The add-on could not be downloaded because of a connection failure on vault.zoho.com "

I have done all the usual checks, if anyone has any ideas how to rectify this problem I would appreciate it.

Windows 8.1 64 bit.

Thanks