Rhino require a license to run (Rhino 8)

You could try what @John_Brock suggests here: RHINO 7 license error - #4 by John_Brock in case you have a corrupt entry blocking the acquisition of a fresh licence.

But I would copy the folders somewhere safe before deleting the contents so you can put them back if this doesn’t help. Note that the reference to Rhino 6 folders is still correct for Rhino 8 - notwithstanding R7 and R8 having their own folders, everything goes into the R6 ones.

After deleting the files try running R8 and it should go through the process of acquiring a licence.

HTH
Jeremy