The "AppMyInterface" service or alias has been removed or inlined when the container was compiled. You should either make it public or stop using the container directly and use dependency injection instead.

# ...
# autowire & autoconfigure: true
# catalogs included

AppMyInterface: '@my.configured.implementation'

my.configured.implementation:
    class: AppMyInterfaceImplementation

$containerBuilder = new ContainerBuilder();
$loader = new YamlFileLoader($containerBuilder, new FileLocator(__DIR__));
$loader->load('services.yaml');

//Make `MyInterface::class` public so
//$container->get(MyInterface::class) should work.
$containerBuilder->getDefinition(MyInterface::class)->setPublic(true);

$containerBuilder->compile(true);