Hi @Joseph , thank you for posting in the Q&A forum.
With all external sharing set to most permissive status, please navigate to your site > Site Settings > Site collection features and find "Limited-access user permission lockdown mode" feature, make sure it is deactivated. After that, test again to see the result.
If the issue remains, please go through the settings one more time as following:
- Set External sharing to Most permissive (Anyone, or at least New and existing guests) via SharePoint admin center > Policies > Sharing. Also remove all restrictions under More external sharing settings.
- Set the external sharing settings for the site to Anyone (or at least New and existing guests) via SharePoint admin center > Sites > Active sites > select your site > Sharing. Also remove the restrictions under Advanced settings for external sharing. You should see different error messages return when external sharing is not properly enabled. If you cannot decide what restriction is set on site level, go with the “Reset to organization-level settings” option at the bottom.
- Enable sharing for site members via Settings > Site permissions > click "Change how members can share" under Site Sharing.
You can also set on Site Permissions page (_layouts/15/user.aspx) > Access Request Settings.
- Once again, check the "Limited-access user permission lockdown mode" feature under Site collection features.
References: Manage sharing settings. / Sharing options are greyed out when sharing from SharePoint Online or OneDrive.
If an Answer is helpful, please click "Accept Answer" and upvote it.
**Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. **