H1 b visa expedited appointment

I am on H1 b visa working in health sector in USA. My previous visa expired last year and currently have a valid I-797 until end of 2022. I need to travel to India for family reasons and trying to make an appointment before leaving US. It says I am valid for Interview waiver but no appointment dates. Chennai consulate said I need to make a regular appointment before asking for expedited appointment. So I picked my visa expired more than 48 months ago. I can see dates available at Chennai consulate but when clicking on dates still says unable to make an appointment.
Anyone please guide through