How to find the reason for a transaction failure using simulation

Summary:

Dear Team,

Our client requirement is to check why one of their document record transaction failed.

So, I opened Manage document records in Approval rules.

There I clicked on Test Rules -> Status as Failed-> Selected our failed transaction and clicked on Simulate.

I got to know the rule name and details but still I did not understand the reason for failure.

I saw this Approval simulation results heading here as shown above but how can I check the reason for failure. Where should I click to proceed further.

Could you please help me how I'll know the reason for failure of Document record submission by an employee.