Agree with Cuppa, if the battery went down over night the Blocking Diodes are probably shot.

You can't test (reliably) a fair few Solar Regs if no battery is connected as they are trying to sense the battery voltage so you will get some weird readings depending on the type of Voltmeter you use etc.

Having said that it does sound like the Reg is U/S as well.

Is there any chance it has had a lightning strike/near miss at some stage?