I have this very same hybrid and I love it because it has probably the biggest flower I ever seen!
This type of paph is generally easy to grow and bloom. Regarding the new fan (growth) not developing any further, did you keep your plant too dry? There must have been something that upset the plant growth.
Yellowing of leaves can be natural, especially when it starts with the oldest, the bottom most, leaf.
How much root did this plant have?
Dark brown can also be normal for paphs. I think I see this more often with plants potting in old bark mix. The dark color is just dirt I believe or stain from the dirt as I do not see this dark dark brown on my paphs planted in fresh bark or other mix.
They might very well be alive though. The best way to tell is to GENTLY feel the roots with your fingers.
If they are somewhat firm (do not squeeze them too hard), then they are alive. The dead ones will be hollow.
How large is bark chips in your mix? I would not use too big particles. It simply dries out too quickly and paphs do not want that. Of course, there is a way around it. Water more often.
Since you mixed in some moss, I think it should stay a bit more moist.
Remember, when the potting mix particle is very fine, the skewer method to detect the "wetness" of the mix is very helpful, but the larger the particle, the less accurate it is.
How many growth does your have? Was there only one growth? How many roots? Usually single growth plant do not yet have many roots.
This is important to know when and how to water your plant.
For paphs with shallow roots, I mist the top inch or so of the potting mix often (even daily as it is dry in my apartment except for summer) because if I were to water regularly, say once a week or once every five days, the top portion where most of the roots are will dry out in one day or two while the rest of the mix stays moist which doesn't do any good to the roots as there are none down there.
Once roots grow all over in the pot, then this may not be necessary, although I do mist the top just a little bit between watering, just not as much.
This paph should stay in bloom at last for one month up to three months. So I think you must have bought yours near the end of its bloom life span.
Each new growth should flower. This can happen once a year until it gets to a certain size, which then will start blooming more often.
I hope yours survive.
Good luck!