The warning messages post-schedule generation (i.e., "Agent is scheduled but not needed...") suggests there is a mismatch between queues, languages, and/or skills from what is being imported and what the actual capabilities of the agents are. The forecast row in the schedule editor, I am assuming to this you are referring, will be empty in this case.
Queue names, skill names, and language names, must match 100% (case- and space-sensitive). Queue names will be validated during import looking at the management unit's service goal groups. Skill names and languages; however, are not validated against actual values during import. So, it is important to make sure these match actual configuration.
You can use the Agents list view to see queue, language, and skill information and compare that with the data in the import.
If you continue to be stuck, I would suggest opening a support incident.