all extensions deleted but yahoo send icon missing in firefox

Additional information In troubleshooting mode, the icon returns as normal. Yahoo mail in Crome browser, with all extensions active works OK and the send icon is shown as normal.

I have deleted all extensions and in Firefox, I cannot see the send icon in Yahoo mail

Thanks for the suggestions.

As said, Yahoo mail worked normally, showing the send icon in a Crome browser.

Some hours later I went back to Firefox and Yahoo mail and to my surprise the Send icon had re-appeared.

I have re-installed all the extensions deleted previously and again, to my surprise, the Send icon is showing normally.

It remains a mystery, but I'm glad all is good again! Yhanks again for your input.