Heres what he says worked in his case:

Empiric solution supposed to work for all devices.

Worked fine for me on 5 different PCs.

Another issue faced by many Windows 10 users after the anniversary update is a dead Cortana.

How to Fix Windows 10 Errors 0x80070057 and 0xa0000400 and Dead Cortana bug

We give you a workaround for that also.

But be sure to backup all your data before embarking on clean installation.

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source: www.techworm.net