No file is created in the assigned multiprocess directory

I've been trying to use multiprocessing mode but I'm struggling to make it work properly.
Even though I set the multiprocess directory, no metric writes any files. I've checked for permissions for writing in the directory and they exist.
I'm currently trying to work with a Gauge in the livesum mode. The metric is incrementing properly within the application but no updates are made available to Prometheus. Is anything else other than setting the directory and a multiprocess mode for the Gauge needed that I might be missing?
I'm using Prometheus inside a Docker container with the port forwarding.

Inizia riproducendo il Gauge segnalato in modalità livesum con la directory multiprocesso configurata, quindi esamina la configurazione multiprocessing e la connessione Docker-to-Prometheus descritte nell’issue. Il lavoro è completato quando viene identificato il motivo per cui non compaiono file delle metriche né aggiornamenti di Prometheus e viene documentata una correzione riproducibile o la configurazione mancante.