welcome to the Polycom Community.
It is always useful to include the currently used software version as issues experienced may already be addressed in a newer release.
This also allows yourself and others to check against current software release notes.
In addition its also useful to explain a few more details like if this is a new installation, an Upgrade, what browser is being used etc.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
There are a number of things that will cause an RMX to say that the key is invalid. First thing I would check is the system information page and ensure that the RMX can properly determine the currently running software version and the RMX serial number. If those are OK then I would need the serial number of your RMX and the version of software that you need the key for.
Issues like this are normally solved very quickly by calling into the support center for your region and opening a Service Request.