License for Zenon 7 and new versions

License for Zenon 7 and new versions

Hi,
Our company has 3 license keys of Zenon 7 and we are currently using Zenon 7.60 version but would like to upgrade to a newer version, such as 8.20 or 10?

We tried to install Zenon 8.20 but our keys are not compatible with this version.
How can we upgrade our current keys?
Thanks