There is an issue with DP uploads at the moment. It looks like the problem is on DP site, their technical support is contacted.
Hopefully the issue will be resolved soon.

UPDATE Jan-17 10:30 GMT: The Depositphotos’ uploads are back now. However, it still looks odd to me:

root@web1 [~]# ftp ftp.depositphotos.com
Connected to ftp.depositphotos.com (178.214.124.65).
220———- Welcome to Pure-FTPd [privsep] ———-
220-You are user number 35 of 160 allowed.
220-Local time is now 09:28. Server port: 21.
220-This is a private system – No anonymous login
220-IPv6 connections are also welcome on this server.
220 You will be disconnected after 15 minutes of inactivity.

Meaning there are already 35 connected users out 160 allowed. Quite sure Lightburner closes any FTP connection it opens, it works this way for all agencies. Furthermore, an opened idle FTP connection will be closed by the FTP server anyway after a certain period of time, like the last line of log stays.
So these are not 35 LB users FTPing to Depositphotos, and I suppose the limit of 160 FTP users is the total limit Depositphotos set on their FTP server for all their customers.
In this case either this agency does not have enough contributors or they just set a too low limit which should be lifted up the sooner the better, avoiding problems like we got yesterday.

Even more odd that Depositphotos guys were unaware about their IT problem until I contacted their online chat yesterday, followed by an email to their technical support. While they fixed their technical issue they choose not to reply me.

The bottom line is, that until Depositphotos expand their FTP limits to more simultaneous connections we are supposed to face this issue over and over.