When the server reaches maximum serving capacity, the website will display this message: "Server is a high-load condition. Reconnect after a while." or "サーバ高負荷状態です．しばらく経ってから再接続して下さい．"
But SinsyPlus doesn't know how to handle this situation and will return an error message "curl: (26) couldn't open file".
It would be useful if SinsyPlus displayed the same error message from the website so I know if that's a problem with the server or my files.