If the tenant does not pay the deposit, the security deposit account will not become active.
It is the landlord's responsibility to make sure that the deposit has been paid and registered before the tenant gets access to the property. Both you and the tenant will receive confirmation from Keyhole when the payment has been registered.
If the deposit has not been paid by the agreed move-in date, you must decide whether the move-in should be postponed or how the situation should otherwise be handled in dialogue with the tenant.