The only problem he is using Braiins OS but maybe it will also work on default s9 firmware. Just try
Both firmware are based on CGminer , so all CGminer commands should "technically" work just fine on any version , unless bitmain disabled that for a reason, which is unlikely.
OP can you please post the exact command you are trying you use?
When i check MinerConfiguration - all data is null (URL=null, worker=null, pass=null)
does this happen after
sched-stop
or after
sched-start