OK with the RCBO unit removed you have no earth leakage protection, over-current protection will still work.
Does the breaker stay on with the selector set to 30mA?
I suspect that the damp has got into the electrics somewhere (not necessarily where the board is located), you need an electrician to look at it and locate where the damp is (clue, it happened after the rain).
Running without earth leakage protection isn't an immediate danger, but it's definitely not advisable for a business.