Free Trial of WP Smush Pro

I have the free version of this plugin and wanted to try the Free trial of the Pro version. I am trying to sync with my single site and I've discovered that a web company had done some work on my site in the past through their Pro WPMU Dev account and I can't now try it myself.

Can you please advise if I can work around this and if not, can you please cancel my Free Trial Subscription.