When I tried to run the following commands

1. php bin/magento module:enable Tigren_Core

Error: Unknown module(s): 'Tigren_Core'

2. php bin/magento module:enable Tigren_ProgressiveWebApp

No Errors.

3. composer require sngrl/php-firebase-cloud-messaging dev-master

Error:

./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Nothing to install or update
Package sjparkinson/static-review is abandoned, you should avoid using it. Use phpro/grumphp instead.
Generating autoload files.

After this one, I followed all the Steps given in the Installation guide. Still, It is not working.