If like me after the setup of your Pixelfed instance you want to import data from your Instagram account, there is a bug with the version 0.12.4 of PixelFed. 😭
After the import of your Instagram's data zip file and the selection of images you want to import, the import queue may be stuck.
It's possible to fix the problem with the following commands in the console of the web container :
php artisan app:transform-imports
chown -R www-data:www-data /var/www/public/storage/m/_v2/
The first command force the import and the second command fix the rights problem that made the imported pics not visible.