Just tested on my set up and it works fine.
Added shaereddomain to shared domain entry
Logged into a test account and added shared.shareddomain.com http://shared.mach-hosting.com/
Logged into another account and added shared2.shareddomain.com http://shared2.mach-hosting.com/
And for fun, made a third one on a 3rd account http://shared3.mach-hosting.com/
All is working.
Maybe you missed a step? Or didn't wait for daemon to run (~5 mins)?
Added shaereddomain to shared domain entry
Logged into a test account and added shared.shareddomain.com http://shared.mach-hosting.com/
Logged into another account and added shared2.shareddomain.com http://shared2.mach-hosting.com/
And for fun, made a third one on a 3rd account http://shared3.mach-hosting.com/
All is working.
Maybe you missed a step? Or didn't wait for daemon to run (~5 mins)?