Disabling TLS 1.0 in the OS for Task Servers breaks Task Management functionality, even with TLS 1.0 unchecked in the Symantec Management Platform (SMP) console.
Usually caused by encryption protocols and/or algorithms not being set correctly in the environment.
This issue is caused by configuration issues in the environment, and not with the SMP software.
Task communications have three components and the issue may be at more than one. The Server running the SMP software, Systems operating as Task Servers, and the individual agents
To better understand the cause, load the Schannel logging on the Notification Server and compare the information with that from a Task Server. If there is no disparity, also check one of the Agents reporting to the Task Server.
This issue has been discussed in the past on similar KBs:
195963 "After moving from HTTP to HTTPS - no Site Server Task Servers are able to register"
172933 "New client machines can't register when only TLS 1.2 is enabled on the SMP server. COM error: An existing connection was forcibly closed by the remote host (0x80072746)"
172653 "Unable to register to a Task Server if only TLS 1.2 is enabled"
162386 "The client and server cannot communicate. TLS version mismatch"