First of all I think you should first try this in the command line:
python manage.py collectstatic
After that go to settings file and check STATIC_URL and STATIC_ROOT
It should look like this(if you didn't change anything):
STATIC_URL = '/static/'
STATIC_ROOT = "/var/www/example.com/static/"
Static Url: URL to use when referring to static files located in STATIC_ROOT.
Static Root:
The absolute path to the directory where collectstatic will collect static files for deployment.
and also you can check the documentation.
python manage.py collectstatic?