Adding this here in case others, like me, are on a shared Siteground hosting platform.
Using the help found here: Free Source Available Invoicing, Expenses & Time-Tracking | Invoice Ninja
On your Siteground account go to Devs > Cron Jobs
type in the code
cd /home/customer/www/yourdomain.com/public_html/ && php -d register_argc_argv=On artisan schedule:run >> /dev/null 2>&1
or
cd /home/customer/www/sub.yourdomain.com/public_html/ && php -d register_argc_argv=On artisan schedule:run >> /dev/null 2>&1
I created mine within a subdomain.
Works great on Siteground. Fast and works with mobile app.