WP 5-minute Install Error: "Waiting on Localhost..." ---why does this happen?

I installed WordPress on localhost using MAMP many times without a problem. Today WordPress froze halfway through a fresh local install and I don't know why.

• Thinking something was out of a date, I updated:
• MAMP to version 4.2
• PHP to v7.1
• After updating MAMP, I upgraded MySQL (prompted by MAMP after upgrade)
• WordPress v4.9.1
• Double-checked database name spelling matches name in ~/sites directory.
• Apache Port 80, tried SQL at 3306 and 8889.

From here, trying the WP install and localhost/SITE-NAME/wp-login.php works fine:

Alright Sparky we're ready to go:

After adding Name/Info/Email/etc clicking "INSTALL", the page hangs here with a message in the bottom left corner of the screen: "Waiting on Localhost...", it doesn't time out and the page-load icon never stops spinning.

It just stays on this screen 'loading'. (I cut the names/emails out of the screenshot, these images makes them look invisible. They are there.) I think I overlooked something. Looking around the web I found someone with a similar problem:

• Problem Installing WordPress Locally (they found a fix, but it doesn't say what answered the problem, only the comment: "its fixed!"

Any suggestions?