May I know the version of Lightroom?
Is it compatible with the version of Lightroom you are using?
Were you able to use it earlier?
It's LR CC (with latest updates) and yes it did work previously. I'm not sure at what point it stopped working as not tried to use it for a while.
Could you please check whether it is compatible with new Lightroom or not?
I've just had a look at this again and it appears is one of the CC updates caused the link to DXO FP3 to be removed from LR (the option under 'Photo>Edit In' no longer appeared). I've just managed to fix this by manually re-selecting and it works fine now - thanks