I had the same problem, and stumbled upon this thread. Also found the solution here: https://studentcommunity.ansys.com/thread/how-can-i-renew-ansys-student-version-license/
I tried all of the above mentioned solutions, and nothing helped. You just have to renew your student licence. It also works if you copy student.lic from new version to your old one. Worked for me, I had 19.2, and copied licence from R3. Thank you @kkanade
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