Squarespace Header Editing Issue

I'm facing a problem with my Squarespace site where I'm unable to edit any part of the header. This includes the logo, navigation menu, and header text. I have already tried troubleshooting by using a different browser but the issue persists.

If you have experience with Squarespace and can help me resolve this issue quickly, I would love to hear from you. Skills in web design and troubleshooting would be an added advantage.