Referring to your reply on Ruchita Mantri's post for the same error on this link (https://www.quest.com/community/products/one-identity/f/identity-manager/27133/getting-error-this-employee-is-not-authorized-to-make-approvals-in-makedecision-method/66233#66233)
My work flow is a bit different and has another level after EX approval step.
The values in my process parameters for EX process-
I have followed all steps as per the documentation but not sure what is missing.
Just a wild guess here. Try to set the parameters of your approval step similar to the screenshot.
If that doesn't work, please contact support.