Alcatel 9400ux IDU fault reason

[jagadeshc]

while upgrading from a 8E1 to 16 E1 calssic IDU
it has accepted in the operational parameters as 16 E1 and sofware key also has been accepted by the Unit. Later it has shown MUX/demux gen.alarm and Config error .which means IDU needs to be replaced.
can any one help out the reason for this error occurance