Here are all important links incl how to post images:
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
I guess that you you have a project from someone else -Is it from LSP?
The plugin is not included in the project-zip, so LMMS cant find it
There are more ways to fix this
1) Find the missing plugin online and add it to your LADSPA folder
This will repair the project, and make it play just as intended.
2) Examine all the FX-tab of all plugins in the project and locate the where the missing plugin is inserted, and then delete it.
That will remove the popop, but the project will be changed and not sound like intended