MFJ = Mighty Fine Junk!

Works great when it works, and when it does not, they require you to send it back and have it repaired at their facilities.

Because you are there and I am here, there is no way for sure to know what you did to break it.

My guess is that you connected it to a transmitter and drove it with too much power and burned it up.

That is what usually happens with the ones that my friends have here.

They forget to attenuate the power at the transmitter before using it and it get fried real easy.

You could check the batteries, but I guess you already did that.

You could also check the PL jumper you are using, I have seen bad jumpers drive people nuts.
Not everyone knows how to solder a PL connector on a piece of coax properly.