Freelander 2 (LR2) Speaker issues

Hope someone can help
Have lost all mid range on radio
I plugged in a trailer for the first time not sure if it was coincidence but sound went after that
Plenty of bass no mid range
Where do I start and what or how to check
Appreciate asking for a lot of information but if anyone can help

Is it the same on cd’s and aux?

Yep
Have done a bit more investigation it seems that all the rear speakers have no sound and the sub in the boot also the same
I believe the amplifier is in the boot on right hand side under rear parcel shelf
Have checked and rechecked all the fuses
Not sure if the amp itself has an in-line fuse etc
Think I will need to take it out
But any help or suggestions would be great