<?xml version="1.0" encoding="utf-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="liip_imagine.async.resolve_cache_processor" class="Liip\ImagineBundle\Async\ResolveCacheProcessor">
            <argument type="service" id="liip_imagine.filter.manager" />
            <argument type="service" id="liip_imagine.service.filter" />
            <argument type="service" id="enqueue.producer" />

            <tag name="enqueue.client.processor" />
        </service>
    </services>
</container>

<?xml version="1.0" encoding="utf-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="liip_imagine.async.resolve_cache_processor" class="Liip\ImagineBundle\Async\ResolveCacheProcessor" public="true">
            <argument type="service" id="liip_imagine.filter.manager" />
            <argument type="service" id="liip_imagine.service.filter" />
            <argument type="service" id="enqueue.producer" />

            <tag name="enqueue.client.processor" />
        </service>
    </services>
</container>

Set as public - resolve_cache_processor
Set as public - resolve_cache_processor

liip_imagine.async.resolve_cache_processor should be public or an exception is thrown when sending enqueue command.