Wilcity Service helps you to update theme and plugin faster. However, it assumes that you installed all plugins and Wilcity before. So, it will remove all plugins in its folder.
To resolve this issue, You should download the full package and install plugin manually:
- Go to ThemeForest.net and log into your account
- Download Wilcity theme
- Extract wilcity-package.zip
- Extract wilcity.zip
- You will see plugins folder, click on it
- Now, pick up your missing plugin and upload it to your site by Login into your site -> Plugins -> Add New