Diego Gaston Arrighi - Thanks for the question and using MS Q&A platform.
If the blob storage account resides behind a private endpoint and blocks public network access, you need to configure network rules to allow communications from blob storage to Azure Event Grid. You can either grant storage access to trusted Azure services, such as Event Grid, following Storage documentation, or configure private endpoints for Event Grid that map to VNet address space, following Event Grid documentation.
For more details, refer to Create a trigger that runs a pipeline in response to a storage event. Hope this helps. Do let us know if you any further queries.