What LMMS version are you using?
If it is anything but the AppImage on our own site, then get the AppImage!
Besides that, since you are new in Forum
Welcome rogantano !
Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
If you like to introduce yourself, to the community, go here:
http://lmms.io/forum/viewtopic.php?f=4&t=4480
Let us know the outcome