Death of Spouse and rollovers

We administer a 401k invested with Voya.  Two trustees, husband and wife; the husband died a few years ago and his account has remained open.  Voya has thus far refused to rollover his account into hers since she has requested.

The plan is the beneficiary and she is the contingent; both are over 59 ½.

Voya is telling me she can not rollover his account into hers for RMD purposes.  Neither are close to 70 ½.

Since he is dead, he can't take an RMD anyway, so what is their rationale?

2 hours ago, thepensionmaven said:

The plan is the beneficiary and she is the contingent; both are over 59-½.

The plan is the beneficiary of what?

The plan is the owner and beneficiary of the contracts.