A user is seeing authentication errors in applications and certificate errors when browsing.

Because the gateway and internal file shares work, the device has basic network connectivity. The two symptoms that remain— certificate errors and authentication errors —share a very common underlying cause: incorrect system time. Quentin Docter explains that certificate problems often come from “ the proper setting of time and date ,” stating that “ The time on the host should always be checked along with the expiration of the SSL certificate.” If the clock is wrong, certificates can appear “not yet valid” or “expired,” triggering browser certificate warnings even when the site is fine.

Mike Meyers also ties time drift directly to authentication failures: “ All clocks—including those in computers—experience time drift… This clock drift can cause problems with time-sensitive applications and services (especially authentication services). ” That matches the exact scenario: apps show authentication errors while browsing shows certificate errors. Duplicate IP or DHCP “bad address” typically causes intermittent or total connectivity problems (which would likely break file shares), not specifically certificate/auth failures. Therefore, time drift is the best diagnosis.