There is no extension able to load the configuration for "web_profiler"

By default, WebProfilerBundle is loaded in dev and test environments only. Find this code snippet in your AppKernel class:

if (in_array($this->getEnvironment(), array('dev', 'test'))) {
    $bundles[] = new Symfony\Bundle\WebProfilerBundle\WebProfilerBundle();
    // ...
}

and append your new environment name to the array:

array('dev', 'test', 'dp')

Very simple in Symfony 4. Just add your new environment to the bundles file.

Open config/bundles.php

Symfony\Bundle\WebProfilerBundle\WebProfilerBundle::class => ['dev' => true, 'test' => true]

becomes

Symfony\Bundle\WebProfilerBundle\WebProfilerBundle::class => ['dev' => true, 'test' => true, 'YOUR_NEW_ENV' => true]