Why can't a chat recipient open a file shared in Teams?

Why the Answer Is Correct

Files shared in a Teams chat are stored in the sender's OneDrive for Business site, and the recipient is granted access through the sharing link created by Teams. When the Limited-access user permission lockdown mode feature is activated on that OneDrive site, OneDrive applies lockdown to items that only have limited-access permissions, so the recipient's permission is effectively stripped and Teams shows "You don't have access to this file." Deactivating the feature — which is exactly what option C does — restores the limited-access permission and lets User1 open the file. This is the documented resolution path and the reason the community unanimously landed on C, including b466dd6 who quoted the Microsoft troubleshooting article stating "This issue occurs because the Limited-access user permission lockdown mode feature is activated on your OneDrive site." C is the only option that touches the actual root cause rather than a tenant-wide policy layer.

Why the Other Options Are Wrong

Option A is wrong because the file storage and sharing options under Teams settings in the Teams admin center control where files are stored and how they can be shared, not per-site permission lockdown; changing them would not restore User1's access. Option B is wrong because SharePoint admin center Sharing settings define tenant- and site-level external sharing behavior, which does not remove the site-collection lockdown that blocks the limited-access permission. Option D is wrong because the Access control settings in the SharePoint admin center govern unmanaged device access and idle session sign-out, neither of which explains a chat file being unopenable by an authenticated internal user. As NaelShoukry suggested with a simple "B is correct," the SharePoint sharing settings are an intuitive but incorrect draw — the lockdown feature sits at the site collection level, below all of those admin-center knobs.

Community Comment Notes

crabb63 kept it short and tied the answer directly to official guidance: "C is correct" with the Microsoft troubleshooting article for the exact error message. b466dd6 reinforced this by quoting the article's root-cause sentence about the Limited-access user permission lockdown mode being activated on the OneDrive site, which is the strongest evidence that C targets the cause. The lone dissent from NaelShoukry pointing at SharePoint Sharing settings is a useful reminder that the SharePoint admin center is where candidates instinctively look, even though the lockdown mode is managed on the OneDrive site itself.