Hey guys hope you're well

I'm having an extremely weird situation with my newly aquired fireface 800.
When playing through the interface Ins and back out again directly through totalmix, everything is fine.

However when I'm using software I get absolutely nothing wether it be through my DAW (Cubase 6.5, upgraded to 9.5 and still no change) or a standalone program like Amplitube for example. No input or output showing on any meters within the software or in the 'software return' section of totalmix. All ins and outs are configured correctly and sample rate is standard 44.1 across the board. All drivers updated, old versions tried. Control room in cubase is off. General PC sound is through completely separate speakers. Still nothing.

I use windows 7 with a Texas Instruments (recommended) PCIe card which shouldn't be an issue seeing as the interface works fine standalone and is always recognised and stable etc, and was used with my previous interface perfectly. I've looked absolutely everywhere for help with this and I spent 5 hours quadruple checking everything today whilst I had a client who ultimately left.

I was getting sound at first but this problem ultimately happened when I changed the buffer size up to 256 from whatever the lowest one is to get rid of crackling, haven't had any sound since no matter what settings I change. Is there some weird tiny thing I'm missing here?

It may be worth noting that the power supply died but was fixed with a recap and is now running perfectly again though.

Plzzzzz help I’ll buy you a beer