I have purchased a trading license, but when I try to sell more than one item, an error window pops up and the item is not registered.
The item was not registered while displaying the error code window.
I ask for help.
Most likely an issue with market items limit. There a limit for unique items on the market which the project team planning to remove sometime soon with one of the upcoming updates, so I would suggest placing for sale only items that already exist on the market so far.