Because it a greedy jerk in costa mesa that owns synchrony.

If you have missed a payment or was late, your promotional period would have been canceled and interest would be added. Could also be that your promotional period has expired, for they only last six months. Paying the incorrect amount can also cause issues. As a rule of thumb that I go by is, pay early and pay above the minimum amount requested. For example if the min payment is $28.00 I pay $35.00 or more. By doing this I ensure I don't get penalized and I pay off the debt early.

It's happening to me too! I'm wondering the same thing