A corrupted system file may cause Windows Defender to fail to start automatically and display an error message with the following description:
Service could not be started.
The requested resource is in use.
Error code: 0x800700aa.
A manual launch also has no effect. Read the steps below to fix Windows Defender error 0x800700aa.
What causes Windows Defender error 0x800700AA?
Damaged files in the system: This can happen to system files as well as any installed program. Conflicts arise that prevent us from using applications normally or even opening them, such as Windows Defender error 0x800700aa.