NSubstitute does not print out NUnit assertion

I have just started using NSubstitute. I mostly worked with Moq, and this is what i was doing:

// In my unit test on menter code herey mock:
HasLogMessage(Is.EqualTo("expected value"));

private void HasLogMessage(EqualConstraint s)
{
    log.Verify(y => y.Error(It.Is<string>(v => Verify(v, s))));
}

private bool Verify(string s, EqualConstraint equalConstraint)
{
    Assert.That(s, equalConstraint);
    return true;
}

Output when unit test is run. Note that it tells what expected and real value is:

Expected string length 14 but was 116. Strings differ at index 0.
Expected: "expected value"
But was:  "real value..."
-----------^
 at NUnit.Framework.Assert.That(Object actual, 

IResolveConstraint expression, String message, Object[] args)

I want to be able to use that with NSubstitute mocks, and here's my attempt at this:

HasLogMessage(Is.EqualTo("Expected value"));

private void HasLogMessage(EqualConstraint s)
{
    log.Received().Log(LogLevel.Error, Arg.Is<Func<string>>(x => Verify(x, 
}

private bool Verify(Func<string> s, EqualConstraint equalConstraint)
{
    Assert.That(s(), equalConstraint);
    return true;
}

But this does not output NUnit assertion error

NSubstitute.Exceptions.ReceivedCallsException : Expected to receive a call matching:
    Log(Error, x => value(IdentityServer3.Saml2Bearer.Tests.Saml2BearerGrantValidatorTest)
.Verify(x, value(IdentityServer3.Saml2Bearer.Tests.Saml2BearerGrantValidatorTest+<>c__DisplayClass21_0).s), <null>, )
Actually received no matching calls.
Received 2 non-matching calls (non-matching arguments indicated 
with '*' characters)

Am I missing something here?