Saber Convertacom SVA NTN5487A - Accessory arm locked in Up

[g8tzl2004]

I have a Saber Convertacom SVA NTN5487A where the accessory "arm" appears to be locked in the "up" position...but with NO radio inserted.

I have tried moving the lever on the right hand side of the convertacom but it does not appear to want to shift the "arm" down so that I can insert a radio into the convertacom. Maybe I need to apply more pressure to the lever?

Has somebody used a key to release the accessory arm and then removed the Saber (there is a lock on the left hand side) but has then locked the accessory arm in the up position?

Do I need a key to release the arm?

Do all convertacoms use the same standard key?

Thanks