The macros you are trying to run is corrupted.While trying to gain access to an object that does not exist.The arguments contain the value that is not valid.The external error like failure to read or write from a file.
There is no exact reason for getting the VBA error 400 in Excel 2016, some of the common causes like VBA corruption or the macros you are trying to run is corrupt and many others.
Why I am getting Excel VBA Error Code 400?
