The logo is not an image file. It is now encrypted base64 based CSS , (basically a line of text based on a picture.)
1. upload your new "logo" to https://thecustomizewindo...-to-Base64-Data-URI/
2. Grab all the information (Height, width and the URL info)
3. find the CSS file here:
lawson\web\lawson\portal\theme\inforControlsCombined.min.css
***PLEASE REMEMBER TO SAVE THE ORIGINAL***
the file has a single line of text.
I marked where to make the changes in the attachment.
search for ##### Change this line
and ##### Change height and width to match the this next line.
4. Paste your logo url
example: url("data:image/png;base64,yourlogotextgoeshere");
5. Remove my comments
6. Save.
7. Log into your portal and see how it looks and tweak it as needed.
PS This css also controls the login Logo as well. Use your browser's F12 Developer tools to find where exactly.