1. Shut down all the nodes but the central
2. Go to programe and features in windows control panel, select Qlik sense and click on uninstall
3. When the unistallation starts a box comes up, click uninstall without selecting "remove Qlik Sense apps, database and data folders".
4. Once the uninstallation has ended reboot and reinstall it (same version that was installed)
5. When all that is finished, you can procede with the the nodes (on parallel if you like) but in this case you will have to tick the box "remove Qlik Sense apps, database and data folders" and "Remove client certificate" (add the service account password if requested)
6. When the uninstall has ended reboot and reinstall the nodes with the previous services
7. Re add the nodes in the QMC (go to the section "Adding a Qlik Sense node" in the procedure https://help.qlik.com/en-US/sense/November2018/Subsystems/PlanningQlikSenseDeployments/Content/Sense_Deployment/Installing-Qlik-Sense-multi-node.htm
Qlik Sense June 2017 and later