Let's get this sorted out by performing some troubleshooting steps so you can change your company logo successfully.
There are times that your browser stores frequently-accessed data, thus causing QuickBooks Online (QBO), to act weirdly. Let's try accessing your QBO account using a private browser to check if it's a browser issue.
Press this shortcut key on your keyboard to open a private browser:
Press Ctrl + Shift + N on your keyboard for Google Chrome and Mozilla Firefox.
Press Command + Shift + N for Safari.
Once logged in, go back and try to change the company logo again to double-check.