Hello choppy,
sth seems to be missing:
"das lässt sich nicht machen" = it is impossible to do so
"das lässt sich nicht leugnen" = it is impossible to deny it (there is no denying)
"das lässt sich nicht reparieren" = it is impossible to repair it
"lassen" in combination with another verb usually means that you let someone else do it (ich lasse das Auto reparieren = I have it repaired I am getting it repaired - by the mechanic)
ich lasse es schreiben ( I get someone else to write it)
so, das lässt sich nicnt +verb says, it is impossible to +verb that/have ... done