I agree that the wiring up to the lot distribution board is OC responsibility. However if the lot owner ( and I’m not suggesting this is the case here) has overloaded the circuit, that’s his responsibility.
On re-reading the original post, it says: ” Our electricity has failed in our unit and our electrician has checked the distribution board and there is nothing wrong with our fuse in that board either. He said there is no electricity going into the distribution board with our fuse in it.”
If there is no electricity going into the distribution board, and the fuse from the distribution board is intact, it’s almost impossible for that to be the lot resident’s fault. In any case, the fix will determine who is responsible and, as we all agree, the priority is to get the supply reconnected then worry about who pays the bill thereafter.