Hi,
There are now several errors where the iMessages account looks logged in but will not send iMessages (On the Mac) whilst the ID actually works on other devices.
I doubt you are singed in fully or properly.
The Status Setting in the Messages Menu is nothing to do with iMessages.
It is about the Status of Buddy Lists.
IF you only have the iMessages account and the Bonjour accounts in the Messages > Preferences > Accounts List AND the Bonjour one is Not Enabled then the item is likely to say "Inactive"
In fact in Yosemite if you disable all other accounts accept the iMessages the Status option disappears.
You can see in this Pic the iMessages account is dark and therefore Logged in and all other are greyed out but there is not a Status item despite the Bonjour Account being selected (out of sight in the list but details on the right).
Do you mean this Details Button ?
It will ask you to Logged in when you use it. (again - as it were if the account is actually logged in).
It will then show you the details and options for your Apple ID in use with iMessages
7:57 pm Sunday; March 8, 2015
iMac 2.5Ghz i5 2011 (Mavericks 10.9)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad