When customer Upgrades from version 20.0 to 20.x ; they are encountering below error.
While performing an upgrade the root cause of the issue could be user is not logged with the Account that is used while Installation of the Product.
1) Go to IIS - Application Pools- Identity - Please make sure to perform an upgrade user is logged in using same account.
2) Make sure correct machine is used for both Server and Worker to perform an upgrade ; this can be checked by Launching Evolve Site as admin - Settings-In the right pane users will be able to locate the machine name where the Evolve Server/Worker and SQL is installed.
3) Also check whether the product was installed using Windows Authentication or SQL User name authentication ; this information should be provided while providing Installation document.
or Can be checked under Webconfig -whether it is Windows or SQL