I've had several sellers never ship the items or bother to contact me, and Mercari will only send so many reminders to ship. Eventually if you can't get ahold of seller than you have to cancel the order and wait for a refund. Some of the sellers sell you fake s*** or damaged and then give you a bad review when you open it and try to get a refund. I wouldn't buy anything that you aren't %100 sure about. Oh and sometimes the app glitches to where it doesn't update the tracking or does it late.