Certificate chain doesn't validate
Check id: tls.chain_invalid · fix effort: medium
What it means
Your certificate can't be traced to a trusted authority. Plenty of devices, especially phones, will reject the connection.
The technical detail
Chain validation to a public root failed, typically a missing intermediate. Deploy fullchain.pem, not just the leaf.
How to fix it
- Install the full chain (leaf + intermediates) on the server. providers ship it as fullchain.pem.
- Retest after deploying.
Does your domain have this problem?
Run a free scan, takes about ten seconds.