I have installed, and made some progress setting up,

I have installed, and made some progress setting up, Appointments +.
However my site has been just a blank screen for the past week or so. White screen of death both on the site and admin - couldn't log in.

To get back in and sort things out I renamed the plugin folder, deactivated all plugins then re-activated them one by one. The culprit was Appointments +. As soon as I reactivate it the site goes back to the WSOD.

Not sure if this is connected, but I'll mention it because it happened around the same time: Hostgator moved my server - nameserver details changed.

How do I get Appointments + working again?