Does vendor have to set notification url in their authorize.net account?
No, you don’t have do to anything on your Authorize.net. The only thing you have to do is just to enter your Authorize.net account’s API credential and keys and that’s all.
Everything else will be handled by Click2Sell.EU. Once you enter this data, Click2Sell.EU servers communicate with Authorize.net servers and process your transactions. We get all notifications about sales, refunds and chargebacks, so if one appears, our system will automatically adjust everything. No notification urls needs to be set up on Authorize.net account for this to work.