Check if the person has an active subscription that gives the right to enter. If there is an active subscription, no clip is drawn and the entry goes under the subscription instead.
If the person is denied entrance, review the validity period of the value card.
Check the validity period in combination with "Permit multiple entrances during the validity period" on the entry product linked to the value card (Configuration > Products > Products)
According to the image above, one clip is drawn when the person first enters the facility. No more clips are drawn for 2 hours regardless of how many times the person passes in and out.