After you configure redundancy, this error message can appear in the logs:
%REDUNDANCY-3-IPC: cannot open standby port no such port
These messages are generated because the Active and Standby Supervisors run different Cisco IOS images.
In order to confirm this, issue the show version command in order to display the software version.
You must make sure that both supervisors run the same image in order to prevent further issues.
In order to resolve this error, either upgrade or downgrade the software of the standby supervisor so that both the active and standby supervisors run the same Cisco IOS software release.
For assistance with the upgrade of redundant supervisors, refer to the article How to upgrade the software images on redundant Supervisor Engines.