Error codes

0x800B0109

A certificate chain ends in an untrusted root

What it means

The certificate is valid, but the root authority that signed it is not in Windows' trusted root store.

Common causes

• A self-signed certificate
• A missing root or intermediate certificate
• An old Windows install without current roots

How to fix it

1. Install pending Windows updates; they refresh the trusted root list.
2. For a company app, install the root certificate that IT provides.
3. Check the date and time; a wrong clock can make a valid chain look invalid.
4. Only remove a certificate in certmgr.msc if you know which program installed it; removing a root certificate can break other apps.