If you were messaging other people's customers, or messaging people who favourited your items or shop... they can mark the messages as "Spam" (because it is).
Too many unwanted messages in too short a time... you get muted by Etsy. It can be a week, 2 weeks, a month... you won't know until the ban is lifted.
There is nothing you can do to change this or shorten the time.
It could also be a glitch. Contact Etsy for answers.
