I cannot upload a logo. I have tried multiple browsers, but when I click on the blank logo space, a dialog box pops up but without the ability to upload a file.

Welcome to the Community, @knagesh. I appreciate all the efforts you've performed to resolve the issue of uploading a company logo. 

I've checked our system and found that we have an ongoing investigation related to this error. Hence, I'd suggest you contact our QuickBooks Support team so they can add you to the list of the affected users. You'll then receive updates about its status through email.

Here's how: 

1. In your QuickBooks Online company, click the (?) Help icon.
2. Select either the Assistant or Search tab to get started.
3. Choose a way to connect with us.

For future reference, check out this article to serve as your guide in uploading, editing, or deleting logos from your sales forms in QuickBooks Online.

I'll be with you again if you have additional concerns or questions about uploading your company logo.