Probability is a standard percentage field on the Opportunity object that indicates how likely an opportunity will close successfully. It is automatically calculated based on the opportunity stage unless you make it editable on page layouts. To allow sales reps to change the probability field value of their opportunities, you need to make the field editable on page layouts. References: https://help.salesforce.com/s/articleView?id=sf.opportunity_fields.htm &type=5 https://help.salesforce.com/s/articleView?id=sf.customize_layoutedit.htm &type=5