GST credit not received

One of my client has not received gst credit for the financial year 2017-18 from a purchase party. My client and purchase party both are GST registered under normal scheme.
The purchase party is not ready to give credit by not putting gst no against my client's purchase.
So now should the credit be reversed and if yes then in current GSTR 3B or in GSTR 9 for FY 2017-18?

or should the gst amount of credit be paid by my client along with interest in GSTR 9?

What should be done now please give suggestions.
Thanking you all in advance.