The restricted picklist error means that the form is trying to create a record with a picklist value that doesn’t exist in Salesforce.
If the submitted value is not identical to the API value name in SF, data won’t be sent to Salesforce. In the forms Submissions section (Failed Applications tab), you’ll receive the following error:
Since 123 Form Builder works with the Salesforce API, it relies on the API Name. No worries, you don’t have to put the API value on the form as a choice. However, you need to provide the API value in the Object Mapping section.
To fix the restricted picklist error, first, you need to check the API values for that picklist in Salesforce.
Then, go to the form Salesforce Integration → Object Mapping, identify the picklist field, hover and click on the Alternative Values icon and provide the exact API values:
In the below example, the Salesforce API values are just codes that mean nothing to the form visitors. I want to display the product name on the form, but the value sent to Salesforce needs to be that code. Therefore, I use Alternative values and make sure to add the values exactly the same as they are in Salesforce, with proper capitalization and no leading or trailing spaces: