This problem occurs when adjustments have been made to the original gift
certificate after purchase in the Inventory>Gift
Certificates>Gift Certificates section. The value has been changed
before the expiry date of a gift certificate product code and/or a new
gift certificate has been written over the top of the old gift
certificate, replacing the original values.
Gift certificates must remain either online or offline for the duration
of the validity period and must remain the same value for that period.
Otherwise you risk giving people who have purchased different amounts in
the past a new gift certificate value.
In summary, it is important that you create a new gift certificate or
clone for each change in your gift certificates. Manage each gift
certificate product line with a unique product code certainly when
changing the value of the gift certificate.
