Error 'There was an error converting the lead’ on Lead Conversion

The following are a few reasons why an error might be thrown while converting the lead:

1. Converting Lead into Existing Opportunity

When Lead is converted into an existing Opportunity, the currency field on the Opportunity record gets updated with Lead currency. It is standard behavior that when Product is associated with Opportunity, the currency field cannot be changed, and hence the user receives the error "There was an error converting the lead. Please try again. If the problem persists, please contact your administrator" if the Lead currency differs from the existing Opportunity currency that the user selected.

To fix the issue, update the lead currency with the currency that is on the existing Opportunity which the user selected on the lead conversion page in Lightning.

2. Field mapped to package that is expired

Lead conversion might fail when there is a custom field that is being mapped to the Account or Contact object and that field is part of a managed package that has either expired or is disabled. Check the packages you have installed for your org to find any that is touching the Lead object and check for any custom fields that are a part of that package and ensure they are not still being used for mapping if that package is expired or disabled. 

3. Discrepancy in the mapped picklist field

This error occurs when there is a mismatch between the picklist values defined on the Lead and those on the target object in the Lead mapping settings.

For example:
Suppose the Lead has a picklist field labeled "Region" with a value of "Oregon", and this field is mapped to the "Region" picklist on the Account object. If the Account picklist does not include "Oregon" as a valid value, the system will throw an error during conversion due to the discrepancy.

To resolve this, ensure that both picklist fields contain matching values or update the mapping accordingly.

4. Flow Error related to automation.

Generate a Debug Log to isolate the issue.

To determine the root cause of the error, generate a debug log during the Lead conversion process. This will help identify which automation or validation rule is failing.

Example:
When converting the affected Lead, a Process Builder flow is triggered to create a new Opportunity. One of the actions attempts to relate an Opportunity Product to a Price Book that is marked as Inactive. This results in a failure during the conversion process.

Use the debug log to trace the execution path and confirm whether the inactive Price Book is causing the issue.
For instructions on how to generate a debug log, refer to Debug Logs in Salesforce Help.

Note: Process Builder is retired as of December 31, 2025. If your automation is built in Process Builder, migrate the flow to Flow Builder. See Build a Record-Triggered Flow