2/3 Trustees missing

I am trying to update trustees for a life insurance policy where three trustees have to act together.

The client is one but the other two are no longer known to them (policy is from the 80s). So it cannot be updated.

We cannot locate either of them via births/deaths/marriages or social media. The insurance provider (Zurich) is proving no advice or direction how to proceed.

Any advice welcome. Thank you in advance.