EPPlus Not Editing Excel File from SharePoint: Worksheets[0] Is Empty

Question

I'm working with SharePoint Client Object Model and EPPlus in C# to edit an Excel file retrieved from SharePoint. While fetching the file and saving it back work fine using OpenBinaryDirect and SaveBinaryDirect, I encounter an issue where Worksheets[0] is empty, preventing any edits.

Here's the simplified code:

// Fetch the file
var filePathSource = "/sites/.../file.xlsx";
FileInformation fileInformation = Microsoft.SharePoint.Client.File.OpenBinaryDirect(ctx, filePathSource);

// Attempt to edit with EPPlus
using (var package = new ExcelPackage(fileInformation.Stream))
{
    if (package.Workbook.Worksheets.Count > 0) {
        var worksheet = package.Workbook.Worksheets[0];
        worksheet.Cells[1, 2].Value = "New Value"; // Edit attempt
    } else {
        // The issue: Worksheet[0] is empty or not accessible
        Console.WriteLine("Worksheet is empty.");
    }

    using (var editedStream = new MemoryStream())
    {
        package.SaveAs(editedStream);
        editedStream.Position = 0; // Prepare for upload

        // Save back to SharePoint
        var filePathDest = "/sites/.../editedFile.xlsx";
        Microsoft.SharePoint.Client.File.SaveBinaryDirect(ctx, filePathDest, editedStream, true);
    }
}

Despite the file being successfully fetched and saved, Worksheets[0] appears empty, and I'm unable to make any edits.

Question: How can I access and edit the Excel file's content when Worksheets[0] comes up empty? Is there a step I'm missing or a common pitfall with EPPlus and SharePoint integration?

Looking for guidance on this issue. Thanks!

Edit: When I save it locally it works fine. But in my case I can't do it. It all should be stored in the memory.