If you're not able to assign OBS or project access...

Check your global security profile. It may be set to something other than what it needs to be to change these elements. Typically if you're assigning users to an OBS, you should be an Admin Superuser.

An Admin Superuser is a global security profile that gives a user read/write privileges for application-wide information and features. The Admin Superuser always has access to all resources. If resource security is enabled, resource access settings are not applicable. To make global information read-only for a user, choose No Global Privileges. The No Global Privileges profile provides read-only access to all global data except costs and secure codes.

Note: Only Admin Superusers can create, edit, and delete other Admin Superusers. You must have at least one Admin Superuser to create other Admin Superusers.

From a consulting colleague….Admin Superuser is a built in global profile. “Administrator” would be a profile created by a user that may have similar rights.