There is a bug for 78XX phones with a 560 series multibase.  https://bst.cisco.com/bugsearch/bug/CSCvw24748The workaround is to use a POE adapter to power the phone.

Since you're running adv. ip services you'd probably want to stick with that.So download the correct ios for your 2821.The file should be c2800nm-advipservicesk9-mz.124-11.T2.bin

Your voice gateway needs to be running 12.4 (11) T2 or higher, ran into the same issue you appear to have. After you upgrade the ios, change sccp ccm 10.16.8.13 identifier 1 to sccp ccm 10.16.8.13 identifier 1 version 5.0.1 HTH.Jared

What version of CM?

Check the file, when downloaded it may come as cisco-ipt-k9-patch5.1.2.1000-11.tar.gz.gz if so change the last .gz to .sgn so it is cisco-ipt-k9-patch5.1.2.1000-11.tar.gz.sgn