If im not wrong then i think i had the same problem before. The banner you want to add the logo on is maybe splitted in 2 parts, so you can only see your logo on 1 of them. So maybe you have to split your logo in to, and add them on each banner part....I know this is very complycated, but it worked for me. but took long time... (im sure it is an easier way)
i just deleted the original logo from the file manager and just uploaded my with the same name as the original logo (logo.png), i didnt go into html at all
right click my logo and "inspect element". it should show you the code and were its located in the css