Zoho Workdrive for CRM doesn't work - error message

Zoho Workdrive for CRM doesn't work - error message

{"error":"App not found","status":false}

already tried different browsers like safari, chrome, firefox.
normally we use chrome.
also uninstalled Workdrive for CRM and reinstalled it. doesn't work either.

Problem exists since monday, maybe since friday, 23rd april.