Error code 0x800705b4 is a Windows defender related error that is a general error and you will not get more details on this error as where exactly the issue lies.
The error may be caused because of two factors:
One can be problems with Windows Defender like issues with running or crashes all of a sudden.
The other reason when the problem with Windows Update doesn’t let you update the system.
You may get an error with Windows Update as it hangs leaving the error. It stops you install updates on the machine and few of them are quite serious for various reasons like bug fixes, security fixes and it is necessary to install them.
Down update manually
In case Windows Update doesn’t update properly on your system then search for the update number of that update that is causing issues to install.
Now move to –Microsoft Update Catalog, and then download the update which is leading to issues.
Once that is complete you can simply open – Downloads folder and then double-click setup file required for update.
Ensure that you perform reboot after that. It is quite useful with large sized updates like Anniversary Update.
Run -Windows Update trouble shooter
Trouble shooters are built in tools in Windows that sometimes try to be little stubborn and do not fix the issues you are facing even after endless attempts.
This issue can be resolved when you run the troubleshooter and it works for a lot of people.
Using your keyboard press- Windows key and type –troubleshoot, now press- Enter to expand it.
Click – View All option available on the left side.
You will get a list from which select – Windows Update located at the bottom. In the next windows click – Advanced and hit– Next.
Click – Advanced, and next, Run as an Administrator.
Ensure that you check the box that says –“Apply repairs automatically “and click Next
Click – Close to complete troubleshooting, in case you want to get more details regarding the issue that is already fixed click – View detailed information.
Delete the folder – SoftwareDistribution
Deleting this specific folder is a common method used often and helps a lot to deal with a lot of issues, because it comprises of files that often corrupt easily and then move on to get rid of the problems present on your device.
Reboot your PC
Press –Windows Key + Press X. Select – Command Prompt(admin)
Typenet stop bits
net stop wuauservCD %systemroot%\SoftwareDistribution
Ren Download Download.old
net start wuauserv
net start bits
Now update Windows.
Disable 3rd party antivirus/firewall
Any 3rd party antivirus/firewall software may conflict with the process of download of Windows Update, so certainly you will not want to disable them and check if you are able to download updates.
You can disable most of them by just right-clicking on their respective icon through taskbar and selecting – Disable.