The primary reason finding a is so difficult today is that the product has been discontinued.
Polycom (now part of Poly, a division of HP) officially designated PVX as End of Life. This means: polycom pvx license key
Polycom required an internet activation process. Even if you had a key, the software would "phone home" to Polycom’s activation server. Those servers were decommissioned around 2015. Modern cracks do not exist because the software is obsolete. The primary reason finding a is so difficult