You are using Cyber Protection Console in a language other than English.
After you edit Windows Defender settings in your protection plan, changes can't be saved. Error message:
422 Unprocessable Entity HTTP/1.1
Request failed with status code 442.
Issue in the product.
This issue is fixed in Acronis Cyber Protect Cloud 20.07.
As a workaround for earlier versions, switch to the English language for console GUI and edit your protection plan.