Answer
Check what you actually entered as the LU name — it should be the base logical unit name only (e.g. CbMsLevel1), not the name with an 'Api' suffix appended (the _API suffix on the package name itself is a separate naming convention, not part of the LU name you reference). Also confirm the package genuinely made it into the dictionary cache — check System Information and Utilities > Logical Units > Logical Unit, or query DICTIONARY_SYS_PACKAGE directly for the LU name — and make sure you've logged out and back in since compiling, since a stale client session can also hide a newly-cached package from the picker.