I can help you get past this error, @useryuxichen.

The stored history in your regular browser can be corrupted and can cause unexpected behavior in the program. Let's try uploading your attachments using a private browser or incognito browser. This way, we can isolate this for a possible browser-related issue. You can use any of these keyboard shortcuts:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Safari: Command + Option + P

If you're able to add your attachments successfully, you'd want to clear your regular browser's cache. Also, you can use other web browsers. You can try running the browser health checkup tool to see if your current browser is compatible with QuickBooks Online.

Lastly, you'd want to make sure that you're attachments meet the specific requirements. Here are the file types you can attach in customer and vendor profiles, as well as their transactions:

• PDF
• JPEG
• PNG
• DOC
• XLSX
• CSV
• TIFF
• GIF
• XML

You can browse this article for more detailed information: Attachments in QuickBooks Online.

Leave a comment below if you have other questions about organizing your transactions in QuickBooks. I'm just a few clicks away.