This error occurs usually when you have mismatch of the dimensions.
In your case the formula for Bonus, Car, Phone costs & Medical costs are currently referred from EMP01 Employee Drivers module(dimensions : G2 Country and E1 Departments; that's the reason the lookup is done to match the country and department.)
I just wanted to add one point that @Jitendra.Vishnolia brought up which is absolutely correct and might be helpful to you as you continue to use LOOKUP, SUM, and SELECT.
For me when I started using these functions, it was helpful to think of modules as tables and the line items that I wanted to use to join as the primary or foreign keys.
So like any SQL join, you have to join the tables by a common key with the same format. The same is true in Anaplan.
If I want to join two modules together using formulas, i need to have a common line item in the same format.
Also , when you're ready, read the best-practice post on DISCO by @DavidSmith . This is by far one of the most important documents written on this subject. This will also help you set up system modules which contain all the "keys" and properties of your lists.
I'm really glad you asked this question. It took me a very long time to get this figured out so I hope you'll continue to ask the Community anytime you get challenged by these functions. Between the best-practice posts and this Community Site is where I learned pretty much everything I know about Anaplan.
Here I am referencing the instructions provided in manual to create the EMP02 module and its formulas as it is provided by Academy content team and facing issue in that. Is there any typo error or missing step in instructions ?