Availability not showing correctly for 1 meeting type

It sounds like the 30-minute service may have some settings that are more restrictive than your other meeting types. I’d suggest double-checking if it’s using custom availability, or if buffers, lead times, or maximum appointments per day are set differently, since any of those can make your calendar look more blocked than it really is. Also make sure the duration is set correctly to 30 minutes, that events on your Office calendar are affecting availability, and that it’s set to “any staff” rather than requiring everyone to be free. A good test is to copy your 15-minute service, just change the duration to 30 minutes, and see if the availability looks right, if it does, then there’s likely a hidden setting on the original 30-minute service causing the issue.

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