Logo Upload Failure

Our logo has been uploaded correctly on our WordPress website for months. Yesterday, I noticed the logo on the website changed in color somehow, so I went back in to fix it. When I tried to re upload the correct logo, nothing happened. Our website now has the “Green Earth” trademark where our logo used to be. I’ve tried uploading PNGs, JPEGS, different versions of the logo, nothing works. What gives?

I am also very new to this so excuse my novice! Any suggestions you have is a tremendous help.