B1/B2 visa appointment (for parents) dates not available

I am on H1B VISA. i wanted to bring my parents to US. I am applying B1/B2 visa.
currently I am unable to find biometric appointments in any locations in india (Hyd, Chennai, NewDelhi, mumbai).
can anyone please suggest.
in the portal it is showing as below .
“Applicants for U.S. visas are required to appear in person for a visa interview at the U.S. Embassy/Consulate. Please schedule an appointment for an interview.
There are currently no appointments available. Please press the Back button and choose a new OFC appointment Date.”.

Even after i select any location, showing the same message . kindly suggest.