What has happened is you have accidently cross threaded the filter and the red flushing assembly. If you have a person with strong hands they will be able to undo this.
If this is not an option then we suggest using a hammer on the protruding part on the top of the red flushing assembly and tap it anti-clockwise until it starts to turn (click here for a photo).
It doesn’t matter it breaks, as it is a one use part and you will get a new one with the next filter.
When you put on the new filter on your jug make sure you screw it on flat and evenly.