New Den. disaster

[Katsols]

Hello everyone! I've never owned a dendrobium so this is my first one. I purchased a dendrobium burana emerald from Ecuador (my country ) that ships for orchid shows in different countries including the U.S. and from the show to the consumer. My orchid arrived with beautiful grass green colored leaves and the roots were in moss without rot and slightly damp.

I re potted it into bark (not very tight) lightly sprayed the roots and placed it on a window that gets evening direct sun.

Three days later I find the leaves yellow like in the picture. Posted before and after pictures.
Now it's down to two leaves! will it come back to life? what to do? the roots look good to my surprise.

thank you!