Hello DoCip,
Thank you for posting in Microsoft Community.
I understand that you are experiencing an issue with Publisher giving an Error 400 code when trying to insert an image into a document. As HTTP Error 400 code usually indicates that there is an issue with the request that is being sent to the server. In this case, it seems that the request headers are too long, which is causing the error.
To ensure that we are on the same page, we would like to ask for few details:
- May we know how did you insert the image?
- If you were to insert an image to Word or Excel, will the issue persist?
- What is your Office license? Is it Microsoft 365 Family, Personal, Business or Office Professional 2019?
- Can we ask for a screenshot of the issue? Please conceal your personal information.
- Is your PC and browser/s updated?
To resolve this issue, you can try the following steps:
- Clear your browser cache and cookies.
- Try setting different browser as default. Guide: Change your default browser in Windows - Microsoft Support
- Check if there are any updates available for Publisher and install them. Guide: Install Office updates - Microsoft Support
- Turn off or disable any antivirus, antimalware, VPN, firewall, proxy and PC Optimizer. The same goes with the browser add-ins.
- Try inserting the image from a different location, such as your local hard drive, instead of an online source.
If issue persists, please provide the answers to our questions above, and we will be happy to assist you further.
Sincerely,
Kathy A.
Microsoft Community Moderator