Hello Musicbear, and thank you for your answer.
Yes I have tried to export it in .wav and .ogg, and both don't work...

Hello to everybody,
I have a little problem : I am using LMMS with a VST (monstrumPulse), it works I can ear it with LMMS but when I export the song I can't ear the notes of this VST (but I can export all the other intruments notes)...
Sorry for my English I am French , and thanks for your help !