Requests are Automatically Declined

We've just started to use Planning at our church and I am finding that after I send invites for assignments, the invites are declined before the user can respond. Is there a setting I am missing or is this a bug?

Head over to WorshipTools Help & Support to provide a list of the emails that have autodeclined: https://www.worshiptools.com/en-us/help#

Tony, I submit a message on the page you directed me to. Thanks.