I'm writing this for my friends behalf because they dont speak english very well,
My x friend farmed gold and traded it to my y friend to sell it for coin.
my Y friend then sold the coin and tried to gift the coins back to my X friend and they got an error that the Y friend only able to send 15 coin to my X friend . The problem is me and my friends didnt see any warning in your coin gifting page and seeing this block feels really frustrating. We farmed that gold for weeks and not able to send the coins to buy his dream weapon makes him really sad. Atleast show me the rules that says one account cant gift ''x'' amount coing to another because there is none as far as i can see.
Coins gained via "Trade" or "Gift" are "Locked" for 72 hours.
This means that for the first 72 hours those Coins can be used only on "Store" and "Service"
After 72 hours they are unlocked and they become usable everywhere.
So, this means that your "y" friend have to way. That is it
my problem is my friend send 15 coin to the other friend , but cant gift another 10 or so the system wont let him gift more coin to the account for some reason. They waited 72 hour as you mentioned