Depending on the type of license that you have, the reason for occurence of this error may vary.
- Individual and Campus-Wide license only - The username in the license file does not match
- Offline Activations - The Host ID in the license file does not match
- Designated Computer Only - MATLAB is already running under a different user account
- Machine has a non-static Host ID
Please refer to Why do I receive License Manager Error -9? - MATLAB Answers - MATLAB Central (mathworks.com), for more details on resolving this issue.
You can also refer to installation - Activating Matlab error: License checkout failed. License Manager Error -9 - Stack Overflow, here the user has decribed some steps sthat you can follow to resolve this issue.