Error in Leave Approval "You cannot approve the leave from EMPLOYEE to Manager yourself"

Dear experts,

When I try to approve a leave request from my inbox, I get the error "You cannot approve the leave from EMPLOYEE to Manager yourself".

I tried for many users but still I get the same message. This is really odd that I get this message. Can anybody predict what could be the possible reason for this issue?

Please find the screen shot for reference

Thanks,

Gourishankar