Jenkins "Create User" fails on Mac OS X High Sierra

Short Summary: The "Create User" form in Jenkins does nothing.

NOTE: I checked other posts related to creating and administering users and saw nothing that clearly describes or solves this problem.

OS = Mac Powerbook OS X 10.13.3 (High Sierra).

First, I installed Oracle Java JDK 8, as specified on the Jenkins installation page.

java -version
java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)

Then, I installed Jenkins, as specified on the Jenkins installation page. (I installed it on localhost/8081, according to directions, because 8080 was already in use.)

Following the directions, it takes me to a screen for "Create First Admin User", as follows...

I entered data to create a new administrative account and selected the "Save and Continue" button. NOTHING HAPPENED. In other words, hitting the button did nothing and kept me on that page.

To get past it, I simply hit the "Continue as admin" button. This allowed me to continue the installation successfully.

After the installation was complete, I went to the "Create User" page with the intent of creating new users.

I entered the new user information and, again, NOTHING HAPPENED. No matter how many times I enter user data (or different user data), nothing happens.

I also shut down Jenkins and relaunched it but nothing happens.

Maybe I'm wrong but it seems that the "Create User" problem is somehow related to the "Create First Admin User" issue.

MY QUESTION: How would I fix this issue in Jenkins on Mac OS X High Sierra so that I can create, both, new administrative and general users?

SOLUTION: This took forever to figure out because there are no error messages or even events in any of the logs. It turns out that when you create the new user, in addition to providing Username, Password, and Full Name, you absolutely MUST provide a full E-mail address "x@y.z". It appears that it doesn't even have to be a real E-mail address (although I would advise against providing a fake E-mail address). If you do not provide an E-mail address, hitting the "Create User" button does absolutely nothing, making it difficult to understand what went wrong. The screen does not change, at all. You get no dialog warnings or errors. You get no info in any logs (Jenkins or System), which is what made debugging this difficult.