Forcing the sale

Good afternoon everyone,

some brief background...
I have a mortgage with a member my family (uncle) on a property in Leicester
when I was 20 I went on a mortgage to remove his wife at the time (Now ex)
between then and now the family have broken down due to deaths and wills (Money).
I'm now 27 and obviously regretting my stupid decisions from 7 years ago.

Now my uncle has gone of the radar, he no longer lives in the mortgaged property and is renting to to someone else, I found this out not so long ago when trying to contact him. his contact number is also offline.

so due to this I went a see a solicitor yesterday and he has informed me to locate the TR1 form for the property to see what arrangements were made back then and also enlist a private investigator to locate him.

now my query is...
I've got a copy of the signed TR1 document and on part 10 of the declaration of trust none of the three boxes have been crossed.
what does this mean? as the solicitor was possibly looking into possible forcing the sale of the property.

Kind regards