http://www.nseindia.com/products/content/derivatives/equities/sec_ban.htm
NSE has banned UNITECH from F&O segment on 19th Sep. I guess zerodha would have complied, that’s it.
Please check the link above to see if the security is under ban or not. The reason is also mentioned there. It seems for Monday 22nd Sep the ban has been revoked by NSE. Just cross your fingers, wait and see zerodha might remove the ban. I am not sure.