Windows Defender Error 577 Cannot verify digital signal

[DianeDG]

I recently uninstalled Webroot (chose not to renew); now I cannot get Windows Defender to run.

When I try I get the following:

Windows could not start the Windows Defender service on Local Computer. Error 577: Cannot verify digital signal; Recent hardware or software change might have installed a file incorrectly or damaged or might be malicious software source unknown.

Don't know how to get Windows Defender to run. Any suggestions?

[HappyAndyK]

If a security software leaves something behind, this can happen. So it is best to use AntiVirus Removal Tools & Uninstallers for AntiVirus programs

Webroot may not have uninstalled fully and properly. Use this tool from Webroot to complete the uninstallation and see if it helps.

See this post for more suggestions: Unable to turn on Windows Defender in Windows 7/8/10