Hi Amy,
The error persists. I have tried all the ways as the following link but it didn't work for me.
using-the-new-qt-htmlconverter-plugin-from-a-plugin-t5465.html
I would like to confirm that everything is working fine for both your windows form and web application project on my server, this issue is happening on the SharePoint project.
Any other solutions or do you have any environment for SharePoint server that I could send you a SharePoint project to replicate the issue?
Thanks in advance.
Lee K