Both R2020a and R2020b exhibit this behavior on our new cluster where you start matlab then do >>parpool(10).
It responds "You requested a minimum of 10 workers, but the cluster "local" has the
NumWorkers property set to allow a maximum of 1 workers"
There are 94 cores available to jobs on each node.
In the Environment / Parallel / Create and Manage Clusters, NumWorkers is left blank which is the default setting of number of cores. The difference with this cluster is that Matlab is built on a VM and not on a compute node, like the older one
Our older cluster responds with:
Connected to the parallel pool (number of workers: 10).
ProcessPool with properties:
IdleTimeout: 30 minutes (30 minutes remaining)