Accessing N/W file using .NET REST API deployed on Azure app service

I am attempting to access a network file share that resides on an Azure VM. The VM has an attached disk used specifically for file sharing. I need to access this file share from a .NET REST API, which is currently deployed on an Azure App Service. (Same Azure subscription)

I have tried using both Azure app services and Azure Container web apps. For all cases it gives couldn't file file. See the code below.

[HttpGet("download")]
public IActionResult DownloadFile([FromQuery] string fileName)
{
    try
    {
        _logger.LogInformation("Download request received for file:- {FileName}", fileName);
        // Network path where files are located
        string networkPath = @"\\filepath\";
        // Combine network path with the file name
        string filePath = Path.Combine(networkPath, fileName);
        // Check if file exists
        if (!System.IO.File.Exists(filePath))
        {
            _logger.LogWarning("File not found: {FilePath}", filePath);
            return NotFound();
        }
        // Read the file as a byte array
        byte[] fileBytes = System.IO.File.ReadAllBytes(filePath);
        _logger.LogInformation("File successfully retrieved: {FilePath}", filePath);
        // Return the file as a downloadable response
        return File(fileBytes, "application/octet-stream", fileName);
    }
    catch (Exception ex)
    {
        _logger.LogError(ex, "Error occurred while downloading file: {FileName}", fileName);
        // Log the exception (logging not shown here)
        return StatusCode(500, "Internal server error");
    }
}