This error occurred when trying to revise the shipping field, which occurs by default when you have all fields selected for revision. There is one shipping method specified: collection only.
I had this error a while back and solved it by starting a fresh template for the auction. However I have quite a few listings and don’t really want to have to workaround it in this way every time I duplicate a historic listing.
Does it work if you revise one of your listing through the eBay website directly? (for test purposes only)
Does it accept “Collection in Person” there?
Yes. Using the revise tool on the eBay website allows me to change it to Collection in Person as the only shipping option. Note that the revise page shows a dropdown menu for Domestic postage with three options:
No postage: local collection only
Courier: large and bulky items
Flat: same cost to all buyers
Obviously I selected the first option. Perhaps Garagesale is not working correctly with this field, particularly if eBay made a recent change to it.