Sigh ... never mind. Once again, my own fault.
Apparently the format of config.json has changed ever so slightly:
{
"UseMysql": true,
"MysqlHost": "localhost",
"MysqlUser": "ark",
"MysqlPass": "xxxxxxxx",
"MysqlDB": "ark_permissions_asa",
"MysqlPort": 3306,
"DbPathOverride": ""...