Item Valuation Change Maintenance

Hello,

I am trying to change the valuation for certain items within Sage however, I am unable to access it as I am receiving an error stating "You cannot proceed with unposted data in Delete and Change Items".

So when I go to Delete and Change Items, I receive the following message "You cannot proceed with unposted data in SO Invoice Data entry". 

I go to SO Invoice Data entry and there is no batches that is open. Can someone assist me to resolve this matter as I am confused to what the issue may be.

Thank you.

P.S. we are using Sage 100