Why am I being asked to purchase more credits even though I haven't reached the registrant limit?

When trying to add new registrants who are paying by check, the system prompts that more credits need to be purchased, although the registrant limit has not apparently been reached. Why does this happen?

The system counts all users assigned the attendee role toward the registrant limit, including those added previously but not paid yet. 

To resolve this, review all users assigned the attendee role to confirm the total count. If needed, purchase additional registration credits to increase your maximum allowed registrants. This ensures you can add new attendees without restriction.