Error codes

0x800b0100

No signature was present in the subject

What it means

The update package arrived without a valid signature that Windows can check, so it is refused before installation.

Common causes

• A proxy or security tool modifying the download
• A corrupted download cache
• A root certificate store that is out of date

How to fix it

1. Reset the update cache: in Terminal (Admin) run net stop wuauserv, net stop bits, rename C:\Windows\SoftwareDistribution to SoftwareDistribution.old, then net start wuauserv and net start bits.
2. Install the current root certificate updates through Windows Update itself, then retry.
3. Download the same update from the Microsoft Update Catalog and check that it installs; if it does, the network is the problem.