The 'Discount Approval Process' did not successfully submitted an opportunity for approval when the discount percentage was set to greater than 0.

@Keerthi Yalamanchili

Possible causes & fixes:

1.  Entry Criteria is incorrect — Check the Entry Criteria in the Approval Process and make sure the condition is properly set to Discount Percentage > 0 (not >= or any other incorrect condition). Also confirm the field API name, for example, that Discount__c is the correct field and not another similarly named field. 
2.  Field Data Type mismatch — If the Discount field is of Percent type, the value may sometimes be stored internally in decimal format (for example, 0.05 for 5%). If you are using > 0 in the Entry Criteria, verify how the value is actually stored and make sure the criteria matches that format. Check the record value manually to confirm. 
3.  Approval Process is not Active — Confirm that the Approval Process has been activated using the Activate button. If it is still in Draft status, it will not be triggered. 
4.  Multiple Approval Processes Conflict — If there is more than one Approval Process on the Opportunity object, check their order/priority. Salesforce may select the first matching process, so another process placed before your discount-based process could be affecting the result. 
5.  The submitted record actually has a blank/zero Discount field — Double-check that the Opportunity being submitted actually has a saved Discount Percentage value. Sometimes the value may appear in the UI but may not be saved if a validation rule prevents the record from being saved. 

Recommended next step: Go to Setup → Approval Processes → Open the relevant process → Check the Entry Criteria section carefully, including the exact field, value, and operator. Then create a test Opportunity record and manually verify the field value before submitting it for approval.