I have a free subscription (Guest)

This error message indicate that the subscription assigned to your Reacts account has expired.

You previously received a contact request by your Healthcare professional: 

Contact your Healthcare Professional for them to give you a free access through their dashboard.

You will then be able to access Reacts again to receive instant messages or a call from your professional.

You were previously invited to a virtual appointment:

An invitation to an appointment gives you free access to Reacts, however this access will expire 12 hours after the scheduled time of your appointment.

Therefore, after these 12 hours, you are no longer allowed to connect to Reacts.

When you will be invited to your next virtual appointment, a new free access will be (automatically) added to your account and you will be able to connect to Reacts again and access your appointment.