It would seem that you are relient on DNS? Have you configured your EM Service URL using a hostname? and also have your left your Enterprise parameters for the directories as hostname?
If so, you have two options ensure that your IP Phone are configures with DNS in order to resolve the IP address, if the host is already added to you Domain of course.
Alternatively configure the enterprise parameter for directories with the IP address of CallManger host and change the EM url with the same IP address.
Hope this helps.
its call manager express(CME), the CME is up and in production all the other phones have the EM and directory features except the 7941 phones.when you click on the service button on the 7941, it does not have the extension mobility like wise if you click on the directory buton, it does not have local directory
Please confirm exact IOS use (complete output of show version) and phone FW, that is accessed by "device status". Also, sometime the phones get corrupted and you need to reset reset them.
Seems that the EM configuration is missing.Here is the link to configure EM in CME.
If you are using SIP image on 7941 then EM will not be supported.
Also verify the IOS compatibility with CME.
As mentioned above, when this happens you have to reset the phone. Possibly, upgrading to a newer FW can fix the issue permanently.