Kindly let us know the current Bagisto version you are using. This will help us identify the issue. Also, please provide images/screenshots of the issue for reference.
This happens because Bagisto expects a default channel before most services boot. Easiest fix is to run the initial migration and seed in isolation by temporarily disabling the API package or commenting the channel call in Core.php, then run php artisan migrate --seed to recreate the default channel, and restore the code after.