Description:
An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details:
Sitecore.Exceptions.ConfigurationException: Could not create instance of type: Sitecore.Data.Database. No matching constructor was found.

Solution:
Sitecore 9 has the new role definition. This issue is due to in appropriate role setup in the web.config file. In my case I had a 9.1 XP scaled setup but on CM the role was default set to Standalone rather ContentManagement. Once switched it worked like a charm. Hope this helps.

Ref: https://doc.sitecore.com/developers/91/platform-administration-and-architecture/en/define-the-server-role.html