The solution here:
BING copilot translated the JSON to HEX and pasted it in the TCP send actor. Worked straight away!
{"jsonrpc": "2.0","method": "system.poweron"}
7b 22 6a 73 6f 6e 72 70 63 22 3a 20 22 32 2e 30 22 2c 22 6d 65 74 68 6f 64 22 3a 20 22 73 79 73 74 65 6d 2e 70 6f 77 65 72 6f 6e 22 20 7d
{"jsonrpc": "2.0","method": "system.poweroff" }
7b 22 6a 73 6f 6e 72 70 63 22 3a 20 22 32 2e 30 22 2c 22 6d 65 74 68 6f 64 22 3a 20 22 73 79 73 74 65 6d 2e 70 6f 77 65 72 6f 66 66 22 20 7d
