Hi. That does sound strange that it won't let you buy the next item up if you've got the item in storage. I bought the x5 seeder without any difficulty (I don't use the fishing boat). Have you tried clearing your browser's cache memory? Perhaps the system is reading old data off your system. It's the only thing I can think of. Otherwise, I would recommend posting the question in the Help section of the forum. One of the moderators might have more information/help for you than I'm able to give.