Any of the following Citrix ADC upgrade operations might cause login failure for local system user accounts:

• from Citrix ADC 13.0-83.x build or later builds to Citrix ADC 13.1-4.x build
• from Citrix ADC 12.1-63.x build or later builds to Citrix ADC 13.1-4.x build
• from Citrix ADC 12.1-63.x build or later builds to Citrix ADC 13.0-82.x build or prior builds

• The user password was changed for the local system user account on the Citrix ADC build (13.0-83.x or 12.1-63.x) before performing the upgrade operation.
• The local system user account was added on the Citrix ADC build (13.0-83.x or 12.1-63.x) before performing the upgrade operation.

Workaround

• Password change from CLI prior to upgrade, will reflect in the new version
• The system root administrator can reset the password for the local system user accounts facing the login failure issue
• Password for nsroot needs to be reset using a single user mode.
  • For more information, see https://docs.citrix.com/en-us/citrix-adc/current-release/system/authentication-and-authorization-for-system-user/how-to-reset-nsroot-administrator-password.html