I have been blocked from the Marketplace and the online buy*sell groups for going on...

I have been blocked from the Marketplace and the online buy*sell groups for going on * months now for no reason. I have not violated any of the community standards or any other policies that are in place. I have been buying and mostly selling on the Marketplace and buy*sell groups for * years now and this is the first time that I've ever had problems like this. I would like for the ban to be lifted and*or an explanation as to why it was placed on my account in the first place. I have lost out on a lot of money from trying to sell things and I've missed out on lots of things that I was interested in buying as well. Not only that, but Lots of things that I was in the process of purchasing from the groups via messages are now gone and it looks to the seller as though I am a fake account or something. So it's ruining my reputation in the groups for being an excellent buyer and seller.