There was a similar thread about this:
https://www-secure.symantec.com/connect/forums/how-add-or-remove-features-existing-symantec-endpoint-protection-client-installations
...definitely remove that ugrade schedule.
- can you check on the properties of one of the clients in your selected group - is there any status under "deployment status"/"deployment message"?
Sylink log would give more information if and why the package has been rejected.