See workaround  

Download via PowerShell

Until enough reputation has been built to convince your organisation, try:-

1. Click “Start” and “Run” (or Win+R) and type powershell
2. In the console, copy and paste the below:-

   (New-Object System.Net.WebClient).DownloadFile((read-host "Paste in the download link"), "$ENV:USERPROFILE\Downloads\")
   

3. Right-click the link on the webpage for the file you previously downloaded and “Copy link address”. Paste it into the Powershell window and press enter
   Eg: https://github.com/phw198/OutlookGoogleCalendarSync/releases/download/v3.0.1-alpha/OGCS_Setup.exe
4. Locate the file in your Downloads folder and run as normal.

See workaround for the installer  

Unblocking the downloaded installer:-

1. For OGCS_Setup.exe you may be able to simply click More info and then Run Anyway
   🔐 You can confirm the file is authentic and safe as it will show the publishers name
   

2. If not, right-click the OGCS_Setup.exe file and select Properties

3. In the bottom right hand corner, click the Unblock checkbox and then OK.
   🔐 Again, you can confirm the file is authentic and safe as it will have been “signed” by the developer
   

4. Execute OGCS_Setup.exe

See workaround for the portable zip  

Unblocking the downloaded portable zip:-

1. After extracting the zip file contents, right-click the OutlookGoogleCalendarSync.exe file, select Properties and then check Unblock as per the images in the above installer section

2. If there is still a problem, try unblocking all the extracted files. The fastest way to achieve this is:-

   1. Winkey+R and type powershell
   2. Change directory to the extracted files
      cd C:\my\extracted\files\directory
   3. Get-ChildItem | Unblock-File
   4. Now run OGCS by double clicking the executable.