Hey Rohit

I am sure that the site must be facing traffic hence the payment is not getting completed. I suggest you to try to complete the payment at late night or early morning when the traffic is less. Also, since you have not mentioned which exam (conducted by NTA) you are referring to I am taking the liberty of assuming that you were talking about NEET form correction fees. Hence I recommend you to contact the authorities if the problem persists at https://nta.ac.in/ContactUs