As the updated calendar system continues to be refined, here's a recommended way too update appointment statuses based on tags, specifically related to the Invalid Status

Part 1: Set up a tag for invalid appointments.

Step 1: Create a tag called "Invalid Appointment".

Part 2: Create a tag-based trigger.

Step 1: Create a new trigger. Under Step 1 in the trigger, set it up like the screenshot above, so that the action will be triggered by the Contact Tag "Invalid Appointment" being added.

Step 2: Set the action to be "Update Appointment Status" and choose "Invalid".
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Step 3: Make the trigger active and save it, in the top righthand corner and save.

Part 3: Using the Tag and Trigger

Step 1: When you have a contact with an invalid appointment, add the "Invalid Appointment" tag and the trigger will run, updating their appointment status to "Invalid".