Error when trying to start application

If your error claims:

Parser Error Message: The 'targetFramework' attribute in the <compilation> element of the Web.config file is used only to target version 4.0 and later of the .NET Framework (for example, '<compilation targetFramework="4.0">'). The 'targetFramework' attribute currently references a version that is later than the installed version of the .NET Framework. Specify a valid target version of the .NET Framework, or install the required version of the .NET Framework.

This indicates that you need to install .NET 4.8 on the server.

You can download ain install the .Net 4.8 runtime here: Download .NET Framework 4.8 | Free official downloads (microsoft.com)

Note that you need to restart the server after the installation.