Another way to trouble shoot errors associated with Amavisd-new, Spamassassin, Postfix, or Clamav is to restart all the services with Amavisd-new being the last one to start:
In this article, I will show you how to use Amavis and ClamAV to scan viruses in email messages. Amavis (A Mail Virus Scanner) is a high-performance interface between a message transfer agent (MTA) such as Postfix and content filters.
This article provides an example of how to configure Postfix + Clamav + Amavisd on Ubuntu 24.04 LTS to enable real-time virus scanning of incoming and outgoing emails.