Thanks for helping to bring this issue to our attention. The message you mentioned is a result of a chance we made to prevent sellers from entering a Packaging & Handling fee when only offering free shipping (since it would be ignored by eBay), but it appears that this change is also blocking sellers such as yourself from entering a Packaging & Handling fee when offering a combination of free and paid calculated shipping services.
Since you should still be able to enter a Packaging & Handling fee when offering a combination of free and paid calculated shipping services, I have forwarded the details of this issue to our technical team and we will work to resolve the issue with an upcoming site update.
I am uncertain when we may be able to resolve this issue at the moment, but I will follow up with you through this thread to let you know once the issue has been addressed or any other pertinent information becomes available.
We apologize for any inconveniences this may be causing. If you need any further assistance with your account, please feel free to contact our Customer Support team from under the “Help” tab on our site and we will be happy to continue working with you.