Error codes

0x800B0101

A required certificate is not valid at this time

What it means

The certificate exists but its validity period does not include the current date, either because it expired or the clock is wrong.

Common causes

• An expired certificate
• The PC clock or time zone is wrong
• A certificate not yet valid after a clock change

How to fix it

1. Sync the clock: Settings > Time & language > Date & time > Sync now.
2. Check the certificate's Valid from and Valid to dates.
3. For a site, contact the owner to renew; for your own server, renew with Let's Encrypt or your CA.
4. Only remove a certificate in certmgr.msc if you know which program installed it; removing a root certificate can break other apps.