Hello,
I’ve downloaded and added the De-Esser plug-in to Audacity and it is now one of the effects I can use.
Problem: When I use it, it causes Audacity to become unresponsive and shuts down on its own or when I try to listen to the adjustment - this error shows up and I have to manually close down the program. 
If someone can help me fix this or provide me with an alternative - that would be much appreciated. 
I’ve downloaded and added the De-Esser plug-in
Exactly what plug-in is that?
When you start using effects that have preview, Audacity has to know how to use both your speakers and microphones. From your picture, neither the record device nor the speaker device is a real thing. They’re software things trying to be hardware.
Is this the setup you use to record sound from the internet? That would do it. Recording internet sound requires folding back sound pathways and it could lead to collisions.
Koz
What are your speakers? You can also get problems if your speakers have a BlueTooth connection.
Koz
The De-Esser is By Paul L.
The speakers are just the ones built into this Asus Laptop.
I had recorded a voice-over demo and then removed the microphone - in order to test some effects.
Thanks for responding, making me feel hopeful over here.
That error is not caused by installing/using a plugin.
Changing the input or output devices, (mic or speakers), can cause it.
Try reverting the microphone set-up to what it was.
That error is not caused by installing/using a plugin.
Changing the input or output devices, (mic or speakers), can cause it.Try reverting the microphone set-up to what it was.
I did what you told me and the same error pops up when I playback the track. Thanks for trying to help though.
Selecting a disabled playback device will generate that error when you attempt to play Audacity …
If the playback device is enabled, try changing the audio host, (there are only 3 options).
I lessened everything on the default settings of the De-Esser and it worked out!! 
Thanks to everyone for taking their time to help me out. Really appreciate it!
Take care and be safe amigos!
Viv