SSL certificate not trusted

Problem: We use a Let’s Encrypt wildcard certificate on our domain.Every time a Samsung device opens up this specific URL (which is a captive portal), the user gets a “SSL certificate not trusted”. But when the device goes directly to the URL(not the pop-up captive portal) everything works as expected, both on Chrome and the internal Samsung web browser It works fine on all other brands.
What could cause this?

It produced this output:
image

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Hi @Jasonjenk

the exact url is required to check that.

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You could also make a packet capture of the connection using a packet sniffer, which would help to reveal what the browser is requesting and what it’s seeing in response. This part of the TLS session is generally not encrypted and is generally visible to a packet sniffer.

If you share the resulting PCAP file, we can also try to understand what’s going on. This is a reasonable option if the service in question isn’t accessible to the public (to run tests using external tools), but it will still reveal the domain name inside the TLS packets.

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The querylog on the DNS server may help well. I wouldn’t be surprise, if the domain name is autodiscover.your.domain or wpad.your.domain.

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