530 Sorry, the maximum number of connections (10) for your host are already connected.
This error is caused by excessive opened connections via ftp. Whenever you are done with online ftp activity then close the connection from ftp properly otherwise it will be connected and some ftp or hosts may have limitations on opened connections. So after exceeding the limit you will no more be able to connect and then you will have to ask your host support from your host. There is a solution though.