session_start is failing to create session ID

I'm working in PHP 7.1 with Laravel 5.5. The error thrown is:

Failed to create session ID: memcached (path: localhost:11211)

The line of code causing the error is a simple session_start();.

My sessions are supposed to be files, which are successfully created:

/config/session.php
  'driver' => env('SESSION_DRIVER', 'file'),

/.env
  CACHE_DRIVER=file
  SESSION_DRIVER=file

So I can't figure out why memcached is pitching a fit or why session_start() is unable to return the ID it is clearly creating.

via Chebli Mohamed