Follow these steps in order. Most users will solve the problem by Step 3.
Rhino’s licensing requires an occasional "handshake" with McNeel’s servers. If your internet is down, or if you are behind a strict corporate firewall/VPN, Rhino may fail to validate your seat. your license is not valid. rhino needs a license to run
To avoid encountering the "Your license is not valid" error in the future: Follow these steps in order
If Rhino crashed while saving license data, the .lic file may be truncated (incomplete). Deleting it (Step 5) and re-entering the key is the only solution. your license is not valid. rhino needs a license to run
If you have tried all steps and still see “Your license is not valid. Rhino needs a license to run” , gather the following and contact McNeel Tech Support :