Why is my SSL certificate untrusted on Android?

The SSL certificate is trusted on most Desktop computers, but only some Android devices. However, even on Android devices where the certificate is untrusted, the root certificate is installed.

I must have tried a hundered ways of resolving this problem, but I think it has something to do with the AddTrust External CA Root (perhaps to do with the SHA-256 fingerprint, which is missing?).

• The cause does not appear to be an incorrect Certificate Authority Bundle.
• The cause does not appear to be related to time.
• All online SSL checker tools I've used (e.g., https://www.ssllabs.com) say the SSL certificate is installed correctly.
• The root certificate is located on my Android device and on my Desktop computer (see the SHA1 fingerprint in the two screenshots, which is identical).

EDIT 1

I believe I have included the new intermediary certificate in my certificate chain, but SSL labs is still reporting that it's not present (even after clicking the "Clear cache" button).

EDIT 2

To be explicit about what I've done:

1. I've signed into to WHM and clicked the "Install an SSL Certificate on a Domain" option.

2. I've entered the domain name "www.angusaustralia.com.au".

3. I've entered the IP address "27.124.127.2".

4. I've entered the certificate issued to me.

-----BEGIN CERTIFICATE-----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HSUEFjAUBggrBgEFBQcDAQYIKwYBBQUHAwIwTAYDVR0gBEUwQzA3BgwrBgEEAbIx
AQIBAwQwJzAlBggrBgEFBQcCARYZaHR0cHM6Ly9jcHMudXNlcnRydXN0LmNvbTAI
BgZngQwBAgEwWAYDVR0fBFEwTzBNoEugSYZHaHR0cDovL2NybC51c2VydHJ1c3Qu
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cmwwgYoGCCsGAQUFBwEBBH4wfDBTBggrBgEFBQcwAoZHaHR0cDovL2NydC51c2Vy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-----END CERTIFICATE-----

5. I've entered the private key (not listed below).

6. I've entered the following certificate key chain (many combinations of the below, but I believe this "longer" keychain should work, as per the discussion on the SSLLabs website). This keychain includes the older "USERTrust RSA Certification Authority", which should be trusted by older devices.

-----BEGIN CERTIFICATE-----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AwIwGwYDVR0gBBQwEjAGBgRVHSAAMAgGBmeBDAECATBQBgNVHR8ESTBHMEWgQ6BBhj9odHRwOi8v
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dgYIKwYBBQUHAQEEajBoMD8GCCsGAQUFBzAChjNodHRwOi8vY3J0LnVzZXJ0cnVzdC5jb20vVVNF
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QWmEOsuc2/jbHyLoryNQq9PHUSngzRmfe7N+iFfqF5p8/sbFUbwQrN4e5yXDagrFakztUlxFXR73
fwIk5Rc9KmIDudq7yqzN68To4sbUpzopPg76AKejfkb3Y8V0yEm2TMsFP2W7d8S6O74TO4PpfR3Q
Ef5KItzX6cWubJ7e2dpRXMaocoLTzTX8ZJlP52/lUN/ALjMOga4aZkRIMY0S1X8w1ywERvkcm63Q
ZnXROlOHmK8cGlHrKaenPnxkipEXhRWoNvlTVVBTH8CjDsaNN+jPMij+feO6mLvXYlNieyW2YU6/
G7lMYVNIDczcFby6xUu1pHuDUAmyS0Qn2snHrevLaFzh60jQ/gfmWO2K2vtwhFQDnUF/dq7M8tfB
vF2g/8yHDsZIJ1t4PGW6sFfqczJhwEf6LdNn/D/ealgg+IYdixjChRsMd1CaavxPXfD6k7U4aX91
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ILjAI7MLPZQY2MnnThQyv6WWAcpxZi4H
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
MIIFdzCCBF+gAwIBAgIQE+oocFv07O0MNmMJgGFDNjANBgkqhkiG9w0BAQwFADBvMQswCQYDVQQG
EwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVybmFsIFRU
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/2CkkeFnvN4ffhkUyWNnkepnB2u0j4vAbkN9w6GAbLIevFOFfdyQoaS8Le9Gclc1Bb+7RrtubTeZ
tv8jkpHGbkD4jylW6l/VXxRTrPBPYer3IsynVgviuDQfJtl7GQVoP7o81DgGotPmjw7jtHFtQELF
hLRAlSv0ZaBIefYdgWOWnU914Ph85I6p0fKtirOMxyHNwu8=
-----END CERTIFICATE-----

7. Now, it appears as if SSLLabs is caching the old result, because when I clear everything from Chrome on my Mac (from the "beginning of time"), the new certificate chain above is detected, as per my previous edit.

EDIT 3

The answer Michael Hampton gave was correct. However, the reason why the solution he proposed didn't work was because WHM has a bug with updating the certificate authority bundle. When this bug occurs, no matter what text you paste into the Certificate Authority Bundle field (on the SSL/TLS -> Install an SSL Certificate on a Domain page), the contents will be replaced with a different CA bundle despite WHM giving you a success message.

Your domain's certificate has two paths to two different root certificate authorities.

On modern desktop browsers such as Google Chrome, as well as on newer Android versions, the path being taken is to the more recent USERTrust RSA Certification Authority root certificate. (I get this on Android 7.0 NPD90G.)

On older Android versions, the path being taken is to the older AddTrust External CA Root root certificate.

On this second path, you are missing an intermediate certificate. This is the one shown in the SSL Labs test as an "Extra download". In order to resolve the problem, you need to obtain this intermediate certificate and add it to the certificate chain in your web server.