Mesh Rig Pivot Point Issue - Maya - Unity

Hi all! Firstly thank you for taking the time to look at this thread,

Now I have created a rig for my legs mesh, I bound the bones to the legs and created some animations it was all working perfectly. All done in Maya

I Imported into Unity as FBX, but the issue that I found is I need to change the pivot point of this model to be much higher.

Now I can change the pivot point in maya but when I try to 'freeze transformations' I get an error that 'Joint 1 has a skin connected to it'?

I have researched and found I should have frozen transformations of the joints beforehand, so I started over freezing all joints and the mesh itself and deleting history. Yet still the same issue as before?

Any ideas? Thanks!