Hi Arian thanks for reaching out! It doesn't look like this issue is occurring on our end. Because this seems to be specific to your Confluence instance I'm going to turn your post into a support ticket and I will be reaching out to your shortly via email to investigate this further.

To any other users if you experience something similar when attempting to use Lucidchart in Confluence please reach out to support@lucidchart.com and we can assist you!