Problem with Matomo database when migrating WordPress including Matomo auto-hébergé

We have a WordPress site including Matomo self-hosted.
Since we migrated WP to another host (using a regular procedure to migrate WP), Matomo is not working properly.
Segmented views are not accumulating data anymore. We have these warning in the diagnostics : Votre serveur utilise un système de fichier NFS.; Il est important de configurer une taille ‘[max_allowed_packet]’ dans votre base de données MySQL d’au moins 64MB. 32MB configuré en ce moment.

Any idea of what the problem may be ?
Thanks for any help !