Matlab keeps asking for software activation even after succesfully activating. How to fix this?

I have version 2017b. This has been working fine until today. Suddenly it keeps asking for activation. When I complete this by selecting the license matlab shuts down and when I try to start it it asks for activation again.... I have a student license. I can download version 2019a, but this will take time and I don't know if this will fix the problem. Anybody have any suggestions?