Why, when maintenance expires, do unassigned products become unusable - despite having perpetual licences to use them?

We had to skip maintenance during a hard time for the business after many years of dutifully handing over many many thousands of pounds.

Some products, for which we have 'perpetual' licences for, were unassigned at the time of maintenance ending and now can not be assigned to any licence - effectively making them unusable.

Mathworks have refused to make a one time only change to allow access to my products.

How can the mathworks 'policy' of not allowing changes to licences out of maintenance be compatible with a customers' right to use products with valid perpetual licences ?