Head Lease not noted on the Freehold Title

Hi, I am in the process of selling my house, it is shared ownership so there are 3 parts to the land registration, all of which are registered however, my buyers solicitor has requested a response to the following: On the freehold title NT590938 , the head lease is not noted on that title . Please obtain clarification why this is the case.

My solicitor requested clarification in April, and chased again recently, is this something you can assist with please? My sale is weeks delayed as a result. thank you 

Good afternoon.
The property in question is 11 Baird Avenue, Forest Town, Mansfield, NG19 0SF.
The headlease title (registered under NT590941) is noted against the freehold title (NT590938) in the current version of the register for title number NT59038.