Fail to enabe shadowsocks.service for invalid argument

[Algebrai]

Operating System

CentOS 7

What did I do

Firstly, I setup the file config.json in /etc/shadowsocks as following:

{
"server":"45.76.xxx.215",
"server_port": 8388,
"password":"your_password",
"timeout": 300,
"method": "aes-256-gcm",
"fast_open": true
}

Secondly, I setup the file shadowsocks.service in /etc/systemd/system as following:

[Unit]
Description=Shadowsocks proxy server
[Service]
User=root
Group=root
Type=simple
ExecStart=/usr/local/bin/ss-server -c /etc/shadowsocks/shadowsocks.json -a shadowsocks -v start
[Install]
WantedBy=multi-user.target

Finally, I run the following commands

chmod 755 /etc/systemd/system/shadowsocks.service
systemctl daemon-reload
systemctl enable shadowsocks.service

and then I get "Failed to execute operation: Invalid argument".

Status of the file shadowsocks.service

The result of the command

systemctl status shadowsocks.service

is the following

● shadowsocks.service - Shadowsocks proxy server
Loaded: loaded (/etc/systemd/system/shadowsocks.service; disabled; vendor preset: disabled)
Active: active (running) since Sun 2023-07-09 17:02:20 UTC; 1h 44min ago
Main PID: 14984 (ss-server)
CGroup: /system.slice/shadowsocks.service
└─14984 /usr/local/bin/ss-server -c /etc/shadowsocks/shadowsocks.j...

What did I expect to see

I expect it could be successfully enabled.