Package dimensions are less than the minimum allowable limit for service {0}

[silverstone1956]

Hi Guys, Anyone else having this issue on Australian ebay. I have been selling on ebay for years and sometimes strike this issue. I am listing a new product and using one of my normal Postage Poliicies- but ebay will not list it and says"Package dimensions are less than the minimum allowable limit for service {0}" . That doesn't even make sense. What...my item is too small for the service?

I am listing it Free Post "Australia Post Parcel Post Parcel (2 to 6 business days) - Free postage" with an Express Post option.