That’s what’s happening in Chromium and IE (on Windows 7):
It claims the root cert is missing:
Note that Firefox shows another certificate hierarchy:
The letsencrypt.org cert sent seems to be valid as it’s the same also received by Firefox:
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
Additionally in IE the site seems to be a bitz broken as the Let’s Encrypt logo seem to be a bit shrinked:
BTW I’ve created a Wireshark log so if you need I could send to you.
Tested using: