Oracle Middleware 12c. Failing to start Application Server after changing Repository passwords

due to server maintenance, we had to stop our Oracle Middleware 12c application server. but startint the weblogic administration server is failing. Admin Server log reports this message

1. weblogic.security.SecurityInitializationException: Authentication denied: Boot identity not valid. The user name or password or both from the boot identity file (boot.properties) is not valid. The boot identity may have been changed since the boot identity file was created. Please edit and update the boot identity file with the proper values of username and password. The first time the updated boot identity file is used to start the server, these new values are encrypted.
2. java.lang.IllegalStateException: Unable to perform operation: post construct on weblogic.security.SecurityService
3. java.lang.IllegalArgumentException: While attempting to resolve the dependencies of weblogic.jndi.internal.RemoteNamingService errors were found
4. java.lang.IllegalStateException: Unable to perform operation: resolve on weblogic.jndi.internal.RemoteNamingService
5. java.lang.IllegalArgumentException: While attempting to resolve the dependencies of weblogic.management.mbeanservers.runtime.internal.RuntimeServerService errors were found
6. java.lang.IllegalStateException: Unable to perform operation: resolve on weblogic.management.mbeanservers.runtime.internal.RuntimeServerService
7. java.lang.IllegalArgumentException: While attempting to resolve the dependencies of weblogic.cacheprovider.CacheProviderServerService errors were found
8. java.lang.IllegalStateException: Unable to perform operation: resolve on weblogic.cacheprovider.CacheProviderServerService

we tried to update our domain repository using the config.cmd tool. actually, we can access all repository schemas (ie: DEV_IAU, DEV_IAU_APPEND, DEV_IAU_VIEWER, DEV_MDS, DEV_OPSS, DEV_STB, DEV_WLS, DEV_WLS_RUNTIME), and all configuration files (under [DomainHome]/config/jdbc) report the correct encrypted password. but, for some reason, the domain administrator user could not connect to Repository DB.
we tried to reset boot.properties file by encrypting domain username/password (running setDomainEnv and java weblogic.security.encrypt tool), unsuccessfully.
can anybody help to fix this issue? thanks