External mono return effect setup in Cubase (RME FF800)

Hi need some help please as struggling to reach my goal.

Using the FF 800 and trying to setup a configuration with a combination of mono+stereo end and returns in cubase (posting same on cubase forums just in case it’s Cubase 7.5 issue)

Bascially I want to use Inputs 1 - 4 as mono inputs/outputs and the remaining input/outputs as stereo inputs

What works :
Outputs 7+8 = Speakers

External Instruments all working using stereo inputs on 1(mono) (xoxbox), 7+8 (JD800), 9+10(JV1080) : works fine
External Effects SPDIF send and return (Fireworx) : works fine

All routed within Cubase as either mono or stereo.
Fireface mixer all set to either mono center or stereo pan left pan right for relevant stereo channels : works fine.

Issue :
Trying to route a stomp box as a send return, same as the fireworx in cubase but as mono.
It appears the signal is not being sent to the external effect. However turning up a generated noise signal from the stompbox, sound is coming in through cubase.

Same setup in cubase but as mono send return.
Same setup in Fireface mixer.

Shows as external effect in Cubase.

However as soon as it’s engaged the TSX303 the sound stops in cubase. I know there’s a routing issue but dont know where it is ie cubase or fireface mixer setup.

What am I overlooking as I am stumped.

No studio setup as direct monitoring from the fireface.

Incidentally I have tested stomp box directly and works fine, same goes for the leads, all tested in the same input but putting the stompbox in the direct audio signal chain. The issue appears to be the send and return configuration.

Snapshots to help diagnose the problem :

http://s974.photobucket.com/user/mfxsound/library/FIREFACE%20AND%20CUBASE

Hi need some help please as struggling to reach my goal.

Using the FF 800 and trying to setup a configuration with a combination of mono+stereo end and returns in cubase (posting same on cubase forums just in case it’s Cubase 7.5 issue)

The main issue is when set up a mono send to a stereo return from cubase using an RME FF800, the sound is muting. Unmute the external effect insert in the strip and sound comes back. So I am wondering if it’s something in Cubase routing rather than the fireface, which I have other effects and instruments working fine.

Any takers? Is it possible to setup a mono send return with Cubase and Fireface, surely?