Blenheim bombs dont explode on ATAG

[notafinger!]

In controls > aircraft, what key or button do you have Drop Ordnance bound to? Sounds to me like whatever key/button you are using is not working.

Just for testing purposes go on ATAG and take a Bf 110 C-7. The console behind the stick will show when the bombs are armed (Ctrl +W by default) and the lights will turn yellow. When you hit the bomb release button the light will go out. If it does not try binding Drop Ordnance to a different key.