The customer disabled TLS 1.0 and 1.1. After that, client machines and the Task Server itself can't register since TLS 1.2 is the only allowed protocol.
Messages like these are noticed while the client machine tries to register to the Task Server:
Entry 1:
Path: /Altiris/ClientTaskServer/Register.aspx
Id: 8.5312
Error type: Network error
Error code: An established connection was aborted by the software in your host machine (10053)
Error note: SocketIOStrategySyncSelect::Send error
Entry 2:
Failed to call web interface by url [https://TaskServer01.yourdomain.com:443/Altiris/ClientTaskServer/Register.aspx?resourceGuid=e2b52c12-a215-44e8-aeea-f979e1ac7cf5&crc=0008000000000EB9], error [0x80072745, An established connection was aborted by the software in your host machine.].
Entry 3:
Could not register using "https://TaskServwer01.yourdomain.com:443/Altiris/ClientTaskServer/Register.aspx"
Entry 4:
An attempt to register on Task Server [TaskServer01.yourdomain.com] over [https] completed with status [FAILED (may retry)].
Entry 1:
Operation 'Direct: Post' failed.
Protocol: HTTPS
Host: TaskServwer01.yourdomain.com:443
Path: /Altiris/ClientTaskServer/Register.aspx
Id: 8.5312
Error type: Network error
Error code: An established connection was aborted by the software in your host machine (10053)
Error note: SocketIOStrategySyncSelect::Send error
Server HTTPS connection info:
Server certificate:
Serial number: 07 15 9e 7a fc 9f b8 c5 bd b0 eb f2 db a1 05 b8
Thumbprint: bf 68 c7 4c b8 5f 40 10 b5 9d 83 dc ec 13 21 42 d3 63 0c 5f
Cryptographic protocol: TLS 1.2
Cipher suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P521
Cipher algorithm: AES
Cipher key length: 256
Hash algorithm: SHA384
Hash length: 384
Key exchange algorithm: ECDH_P521
Key length: 521
-----------------------------------------------------------------------------------------------------
Date: 10/8/2018 10:36:54 AM, Tick Count: 121945 (00:02:01.9450000), Size: 1.01 KB
Process: AeXNSAgent.exe (5312), Thread ID: 5604, Module: AeXNetComms.dll
Priority: 1, Source: NetworkOperation
Entry 2:
Failed to call web interface by url [https://TaskServer01.yourdomain.com:443/Altiris/ClientTaskServer/Register.aspx?resourceGuid=e2b52c12-a215-44e8-aeea-f979e1ac7cf5&crc=0008000000000EB9], error [0x80072745, An established connection was aborted by the software in your host machine.].
-----------------------------------------------------------------------------------------------------
Date: 10/8/2018 10:36:54 AM, Tick Count: 121945 (00:02:01.9450000), Size: 530 B
Process: AeXNSAgent.exe (5312), Thread ID: 5604, Module: client task agent.dll
Priority: 2, Source: Client Task Agent
Entry 3:
Could not register using "https://TaskServer01.yourdomain.com:443/Altiris/ClientTaskServer/Register.aspx"
-----------------------------------------------------------------------------------------------------
Date: 10/8/2018 10:36:54 AM, Tick Count: 121945 (00:02:01.9450000), Size: 350 B
Process: AeXNSAgent.exe (5312), Thread ID: 5604, Module: client task agent.dll
Priority: 2, Source: Client Task Agent
Entry 4:
An attempt to register on Task Server [TaskServer01.yourdomain.com] over [https] completed with status [FAILED (may retry)].
-----------------------------------------------------------------------------------------------------
Date: 10/8/2018 10:36:54 AM, Tick Count: 121945 (00:02:01.9450000), Size: 369 B
Process: AeXNSAgent.exe (5312), Thread ID: 5604, Module: client task agent.dll
Priority: 4, Source: Client Task Agent
ITMS 7.6, 8.x
This is a Microsoft configuration. There are certain places in the registry that sometimes need to be modified to force TLS 1.2 to be the only one in use.
See:
https://docs.microsoft.com/en-
https://support.microsoft.com/