クラッシックのページになる、Lightning Experience 切替できない

For the other user's profile or via permission set assign this access and check

Setup > Home > Users > Profiles > The Profile's Name > Edit > Administrative Permissions > Check Lightning Experience User > Save

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Improve Data Quality for a Recruiting App -Create Validation Rules" でクラッシックになる？

You can't view this item in Lightning Experience. Open in Salesforce Classic.