Please follow the steps given below .

  • Open IIS on your system
  • Go to Application pools and check the ASP.NET V4.0
  • Run command prompt as Administrator
  • Run the command  C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe –u 
  • It will start uninstalling ASP.NET v4.0.30319
  • Run the command  C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe –ir
  • It will start installing ASP.NET without changing the existing web applications  
  • Restart your IIS

Please go through the below given screenshot for further reference: