Dropbox Online-Only files and C# FileIO Access - file-io

Question

I have a folder that has thousands of files in it so i have Dropbox sync it as "Online-Only"
I've written a C# dotnet7 app to copy specific files to a separate folder.
foreach (var aFile in Files(srcroot))
{
var destFileName = #$"{destroot}{aFile.Name}";
if (!_fileSystem.File.Exists(destFileName))
{
_logger.LogInformation($"Copying File {aFile.FullName} -> {destFileName}");
_fileSystem.File.Copy(aFile.FullName, destFileName);
}
else
{
_logger.LogDebug($"Not Copying File Dest file already exists <-- {destFileName}");
}
}
But Keep Getting the same error messages
System.IO.IOException: The file cannot be accessed by the system. : 'C:\Dropbox (Personal)\Camera Uploads\2023-01-24 13.28.50.jpg'
at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options)
at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
at System.IO.Abstractions.FileWrapper.Open(String path, FileMode mode, FileAccess access, FileShare share)
at Service.ImageCopier.Run() in C:\Users\mark.greenway\Desktop\Repos\DesktopToolsService\Service\ImageCopier.cs:line 64
at Service.DesktopToolsWorker.ExecuteAsync(CancellationToken stoppingToken) in C:\Users\mark.greenway\Desktop\Repos\DesktopToolsService\Service\Worker.cs:line 44
If I open the folder in Windows Explorer it downloads and copies without issue.
Is there a way to open or copy a file that will trigger the Dropbox "Online-Only" to download?