wpmudev-updates plugin won't allow sign-in

I moved my website to a different hosting company and now I am unable to sign into WPMU via my sites WPMU Dev dashboard. It was previously active. The "Upgrade pop-up" is displayed thus preventing any further action on this page. The "manage" screen is not much use and shows the following i message: "Only the admin user "XXXX" has access to the WPMU DEV Dashboard plugin and features on this site".

I've de-activated, re-activated and deleted and re-installed the plugin with no success.