SEP Client can't contact SEPM
I'm using SEP 12.1 small business edition, some of my clients can't connect to SEPM.
I already tried to troubleshoot from the client by clicking HELP->troubleshooting->connection status->connect now and I got error 12031. I check the log and it says unknown error. I search on the internet and have solution, but it is for 11.x version, which modify the bandwidth limit on IIS.
Some of the client can connect, but after a few days it lost the connection to server and I need to connect to server manually by following the troubleshooting step. How many clients does SEPM 12.1 can manage? Anyone ever meet this error before?