Windows Defender real-time won't turn on after failed update on 8.1

[KarelVraždička]

Update on windows update failed, now windows defender's real-time protection won't turn on, I have no other antivirus, haven't had it for the longest time and defender worked the whole time. I tried to reset windows update and run the updates again, which worked and they installed without problems but it didn't solve the problem with defender.

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