Cube exceptions are not visible in planning workbench, if constraint naming convention is not followed properly in XML file.
For Constraint(in Constraint XML file), display name should be same as constraint name with " " in place of "_ " in constraint name. e.g display name for "Plan_Analysis" should be “Plan Analysis”. Otherwise it is better not to mentioned display name for constraint name IOP code will take care of it then.
After doing above changes, do bootstrap.
I hope this will solve your problem.