I'm a beginner when it comes to orchids but just by
the look of it i would say "its rotten"
try cuting off the leaf check for root rot put hydrogen peroxide
On the fungus everyday till it stops bubbling then after
That put cinnamon to stop the spread of the fungus.

O.o I didn't want to unpot it since I had just potted it a couple months ago but I'm SO glad you brought it up. I decided to take a look and most of the roots are gone. It's in fir bark with a net pot so the rot must have already been started when I potted it. Yikes, it only has a few roots plus some nubs.

Take a straight edge and cut the bulb until you reach clean tissue. Put some alcohol on the straight edge to sanitize. After cutting, put some cinnamon on the cut edge and leave the plant alone.

Put in a sunny window, water, fertilize and it should be fine. It is the time of year when the plant is making new growth so all is not lost.

Just watch the cut area that it doesn't continue to turn black.

Jane