This happens because the CONTENTdm Administration Users page has reached the display limit of 200 accounts. Accounts that do not show up in the list can be manually retrieved by navigating directly to the desired user name:
https://server#####.contentdm.oclc.org/cgi-bin/admin/showperm.exe?CISOUSER=username
in your browser URL barIf the user name is not configured, it will return the message "User user name not found."
A complete list of configured user names and permissions can be provided by OCLC Support.