Lead Validation Rule not working when converting Leads.
|Knowledge Article Number||000176187|
|Description||If you are converting Leads and you wanted to enforce the Validation Rule, you need to enable "Require validation for Converted Leads"
If the said setting is not available, please contact Salesforce Support to enable the "Use Apex Lead Convert" permission.
|Resolution||To enable the "Require validation for Converted Leads"
For information on Enabling 'Use Apex Lead Convert', click here.