Try each of these separately:
Close all your browsers, re-open and try again.
In Chrome, try clicking the ">>" (more) icon on the top of your browser to see if Chrome hid the Blasty icon there.
Try to resize your address bar by grabbing the right hand side of it and pulling it to the left. This may uncover the Blasty icon.
Open your extension page ("Tools | Extensions"), then disable and re-enable Blasty. If there's a 'Show Button' button in the Blasty section of the extensions page, click that button.
If this did not work for you, please reinstall Blasty from your dashboard or contact us here.