Users are unable to sign into the product

We have multiple users getting "no internet connection" when attempting to sign into the product.
We've tried removing anti virus and disabling firewall, internet is working normally for all other apps.

Rebooted the machines and reinstalled the product didnt help, when prompted in the application to update the update fails with "invalid signature".

Sorry the full product/Version is PDF Architect 6.. this is a pro subscription but the end user doesnt have the tech support email address to email.

Just to confirm we uninstalled the product fully, reinstalled from the web downloader and this was resolved.