Understanding that you are using the same adresses for the tacacs server, are you also using the same ip adress for the router?
I suppose that this is not the case but you are trying to add a second router to the network?
If so, looking at the logs, it could be that the second router has not been added as a NAS in your Tacacs server database. Hence Tacacs does not "trust" this 2nd host and refuses to authenticate for it.
regards,
Leo
