I wanted to give an update, just to confirm what @remedios told me
It's 2 weeks that syncrony blocked my use of the card, i've made a payment on 1st of november and even if the statement is updated they put an hold on the money. Basically i have a 0 balance but also a 0 available credit so it's 20 days i can't use the card.
They told me that the card is fine just i have to wait for the release, every other day the say to wait 24-48 hrs but nothing change.
They explain me that the hold was put because of unusual payment pattern.
in the end i simply can't use the card 