Cannot log in to Outlook

Bryan 20 Reputation points
2026-03-28T12:49:56.8533333+00:00

When trying to log into Outlook I get the error below. I have strong wifi and I am connected to the internet. I have tried logging in on multiple networks. I have unistalled and reinstalled all Office programs, including Outlook. I have restarted my computer multiple times. I am receiving emails on my phone, so it is not an issue with my Outlook account. It is specific to this computer. User's image

Outlook | Windows | Classic Outlook for Windows | For home
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Answer accepted by question author
EmilyS726 280.2K Reputation points Independent Advisor
2026-03-28T13:24:51.63+00:00

Can you go check your Windows Settings > Windows update, and see if you might have  KB5085516 available to install?

KB5085516 was released on March 21st to address Microsoft account sign in issue among some apps caused by KB5079473 https://support.microsoft.com/topic/march-21-2026-kb5085516-os-builds-26200-8039-and-26100-8039-out-of-band-09e85404-1cb6-4ed4-9ca5-3e40d74307b9

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  1. AI answer

    2026-03-28T12:50:10.43+00:00

    On this specific computer Outlook and other Microsoft 365 apps are likely failing to activate or reach Microsoft 365 services even though general Internet access works. This matches the scenario where Office apps report no Internet and cannot sign in while Wi‑Fi works.

    Follow these steps on the affected PC:

    1. Update the wired/wireless network adapter driver
      • Open Device Manager.
      • Expand Network adapters.
      • Right‑click the active adapter > Update driver and install any available update.
      • If Windows Update finds nothing, download and install the latest driver from the PC or adapter manufacturer’s support site.
      • Restart the computer and try signing into Outlook again.
    2. Disable IPv4 Checksum Offload on the adapter If updating the driver does not help:
      • Open Control Panel > Network and Internet > Network and Sharing Center > Change adapter settings.
      • Right‑click the active network connection > Properties > Configure.
      • Go to the Advanced tab.
      • Locate IPv4 Checksum Offload (or similarly named option).
      • Set it to Disable.
      • Select OK, then restart the computer and test Outlook sign‑in again.

    If the issue is resolved only temporarily after disabling IPv4 Checksum Offload, work with the network adapter/PC manufacturer or Windows support to obtain a permanent fix (for example, a corrected driver or firmware update).

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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