Thanks for reaching out for support here in the Community. I'm here to provide some additional info so you're able to upload your company logo.
In addition to the steps you've tried so far, it's always a good idea to clear the browser cache. Sometimes the cache can get full of older stored data, which can potentially cause viewing and performance errors within the system. Clearing it will get everything back up and running smoothly. For example, here's how you'd do this in Chrome:
1. Click the three vertical dots in the top right corner.
One other method to fix the problem with the logo not uploading is to save it as .jpg. You can do this by opening the logo in Microsoft Paint, choosing Save As, then saving with a different file name and as a .jpg. The following link covers adding, customizing, or removing logos on sales forms.
Please don't hesitate to reach back out if you have any other questions. I'll be here to help.