Hi Audrone,
Thanks for posting here.
I realize you are using Small Businesses for Office 365, and you encountered 404 not found issue when you clicked the “Edit website” button on the Admin page.
Based on the situation, I would like to confirm with you about the following things to help us narrow down the issue.
1. Could you access your team site? If so, please check if you can access the edit page directly by manually typing the URL in Internet Explorer browser: append the URL of your site with /Pages/Forms/AllItems.aspx, for example, youdomain/Page/Forms/AllItems.aspx.
2. Did other admins encounter the same issue or just special one?
3. Whether the issue occured on other machines or just special one?
It will be nice if you can post screenshot about the error message here.
Thanks,
Maggie Li