Error catalogueThe signed client assertion
Generic client authentication failure
What it means
The server reports a generic failure that covers many assertion problems.
Fix
Fix any failing local checks; then compare the server registration (client_id, JWKS/kid, key).
Seen on real servers
{
"error": "invalid_client",
"error_description": "Client authentication failed"
}Check it with smart-doctor
Run your login and smart-doctor ranks this cause against the others, with the evidence it found.
npx smart-doctor check my-profileAlready have the server’s error? Explain it without running anything.
npx smart-doctor explain '{"error":"invalid_client","error_description":"Client authentication failed"}'