Hi Nikola,
After my domain was transferred to a different datacenter (with the same hosting company) I encountered the following issues:
e-mail (requesting appointment) received before/during the transition when I was clicking on "confirm appointment" would produce "Invalid token" error.
Now, when the transition is complete the e-mails from Easy Appointment would not be reaching nominated e-mail address at all. But the e-mails are been sent by the plugin as I can see then via console. Please help. Thanks.