The formation of the first JF-17 squadron was delayed by almost two years, as it was originally to be formed in the mid 2008. But as the saying goes, "der ayad durust ayad".
engine issues!
Finances!
The first squadron was to be formed in late 2008, but govt. had no finances.
So the PAF had to wait till credit facility became available to them by the Chinese govt. The current planes (the first 50) are being bought on seller's credit.
People here do not realize how financially strapped the PAF (and the entire country) has been since the new govt. took over. And you see members arguing for 100 Rafales here when even a low-cost JF-17 is enough trouble.
A big thank to China also goes here.