Having the same problem. tried typing 'arx' too. Options are [Files Groups Commends Classes Services Load Unload]. Any ideas?

If the TBAR command isn't bringing it up and your certain cadMEP is loaded, then try switching your workspace and trying TBAR again.

If that doesn't work you can try closing AutoCAD, deleting your AWS profile files found in:

C:\Users\YOU\AppData\Roaming\Autodesk\AutoCAD 2017\R21.0\enu\Support\Profiles\

The problem is unlikely to be with Autodesk Fabrication and you may ultimately have to re-install AutoCAD, but try a repair first.

Unfortunately still no joy. Haven't ran a repair from installation but did install SP1 & update. (How do I run a repair?)

Tried turning off & on again. tried deleting AWS profile. Tried changing workspace +TBAR.

This did happen before on me but can't remember how or why it happened. Frustrating. Can work around it using the CADmep right mouse click but it is cumbersome to say the least.

Well,

If it's not a workspace, not a profile and cadMEP is loaded, then something has to be broken and not just misconfigured. You can try the repair, but your CAD gremlins may very well be stronger than a repair can fix. So, if this repair process doesn't fix it, then you will have to technically reinstall AutoCAD. Which can also be done through the repair dialog, but it may need a complete uninstall -> reinstall from scratch if it persists.

FYI, The Fabrication tool bar is 100% dynamically created; it even reloads while CleanScreen is actived. It isn't backed by any traditional CUI elements and thus should be there unless something is pretty broken. 

To do a repair:

Open up the programs and features part of Windows, find AutoCAD, right click and select Uninstall/Change in the context menu; just follow the dialog from there.

@Anonymous 

Many thanks for your quick reply.

Was going to repair as a last resort but before I tried to repair first thing this morning ,I opened up Fabrication CADmep and alas, my 'Attacher' TBAR appeared! This happened me before but still have no idea how Autodesk rectified itself overnight, but it did.

Much respect to you for your help.