After your suggestion, I decided to give it another try, and messaged the last one on LINE.
Does it come as a surprise that 5 days later the message still hasn't been seen, and the interested seller hasn't returned to FB either, and even deleted the whole conversation. She messaged she was interested and ready to transfer.
I just got another one with the request to add them to LINE, that is now 8 in total.
My observation is that all those are ladies, although the article I have for sale isn't something catering to females.
When I click on their FB profile, it is either locked, or they have 4 friends.
Obviously there is more to this than what meets the eye