I installed the Unity Hub. But one error message appears while running the program.
How can I solve this problem ?

I cannot hold on my works because of this problem.
I installed the Unity Hub. But one error message appears while running the program.
How can I solve this problem ?

I cannot hold on my works because of this problem.
You doesn't have a license, hence quite straightforwardly you should search for "How to activate a unity hub license or something"
if you are using unity hub 3.x: