Error -12: Maximum number of concurrent users reached (4D Client)
You are trying to connect to 4D Server using 4D client but the system doesn't let you. Every deployment of 4D Server has a maximum number of concurrent users. If you try to connect more users than you have licenses for, then system will not let you. In that case, you have to either purchase an additional 4D Client Extension license or simply ask one of the other users to quit the program so that you can connect.