There are a large number of dynamic disk volumes on your DPM. The number of volumes after this Create-PG/Modify-PG would ...

There are a large number of dynamic disk volumes on your DPM. The number of volumes after this Create-PG/Modify-PG would have been %CurrentVolumeCount; while the DPM upper limit is only %MaxVolumesThreshold;. Hence this operation was disallowed.