To all this is something on Pixieset site and has nothing to do with LrC.
The error is coming from that publish service. You are OUT of allowed storage space on that service.
In the future, So people don't have to download the image you have attached, please use the Insert Photos icon found in the Tool Bar of the Post and Reply text entry dialog window as pictured below. Since you Can't Edit your original post to remove the Attached screen shot Please include the screen shot you attached to a new reply to this conversation by clicking the Blue Reply button under your original post and use the Insert Photos icon in the tool bar. The Insert Photos icon is this one in the Tool Bar.