I doubt that a Workstation 15 key will work with the Workstation 16 software, given that VMware sell upgrades.
https://store-us.vmware.com/upgrade-to-workstation-16-pro-5424179100.html
-------------------------------------------------------------------------------------------------------------------------------------------------------------
Although I am a VMware employee I contribute to VMware Communities voluntarily (ie. not in any official capacity)
VMware Training & Certification blog
