Also, Pleaes check if cost center you want to plan is blocked for primary cost planning. The block may be set in the master record of this cost center for the period(s).
Try following and see if this works
- Do not plan primary costs for cost center at all (you will not agree)... or
- try to plan period in small number like try for 2 months and so to see if cost center is open for primary planning in new perioed.... or
- Check if cost center is not block.
Thanks,
Naseem