If using S4S in a multi-lingual Sitecore installation, we highly recommend enabling language fallback for both items and search indexes.
There are some language-specific situations where a form may not appear in the S4S Sitecore Form Mapping Wizard.
Submit Action reference item
The Mapping Wizard can create mappings for any form, but only displays the relevant ones in the on-screen list. By default this includes any form with the S4S Generic Submit Action, but may include forms with other submit actions as defined by items in the following path in the master database:
/sitecore/system/Modules/S4S/SitecoreExperienceFormMapping/SubmitActions
When loading children of this item, Sitecore provides only those for the current language. If you do not see your form, you can either create a language-specific version of the item that references the submit action or set an existing one as a fallback for all languages:
Form language
The Mapping Wizard only displays forms whose language matches the value of the current Sitecore.Context.Language. If you do not see your form, check the language(s).