I got error while going to a page such as login after I have enabled google recaptcha

This Error --
An unhandled exception occurred while processing the request.
NullReferenceException: Object reference not set to an instance of an object.
Grand.Framework.Infrastructure.Extensions.ApplicationBuilderExtensions+<>c.<UseGrandExceptionHandler>b__1_1(HttpContext context) in ApplicationBuilderExtensions.cs, line 90

Which version of GrandNode do you use?

Edit. I found an issue in GrandNode 4.40, but it's develop version, so it may contains bugs. We will fix it before official release.

Best,
Patryk

Which version I should use?

It's always the best to use the latest released version. So in the current situation GrandNode 4.30.