Some suggestions are in this thread, though it appears you have already seen it.
https://community.ebay.com/t5/Mobile-Apps/How-to-Block-unsolicited-offers-from-sellers/m-p/34512789#...
Changing your communications preferences may not affect the messages you receive instantly; it may take a while for the new preferences to prevent new messages.
Other than that, you should look at the filtering suggestions if you want to keep your email inbox clear, or else provide eBay with another email address altogether.
