What the developer didn't explain adequately, and what I'd like to explain to help other users, is that in order to export your settings before uninstalling, you have to bring up the Options window and then go to each individual email account that's listed and click Export. I was not able to find that because the developer didn't give details. So I was not able to save my settings before uninstalling. But when I reinstalled it, it seemed to pick up some of my earlier settings anyway. I reconfigured everything manually just in case, and now I'm up and running again. (BTW, if nothing else works to find the Options window, you can go to your Firefox Add-ons and find X-Notifier and click on the Options icon. That was the only way I was able to do it because the X-Notifier toolbar was not working before I uninstalled the add-on.)
Version.... 46
Sometimes you need to check more than once for updates.
My FF version is now 46 ...and I don't think it's a developer or beta.
But then also... you could export (backup) your accounts, then try re-installing X-Notifier.
V 46
I just uninstalled and reinstalled -- that solved the problem
Uninstalling & reinstalling
Uninstalling & reinstalling did the trick. Thank you.
Sorry for the FF version confusion. It's indeed ver 46.
Before uninstall/reinstall - how to find Export/Import
What the developer didn't explain adequately, and what I'd like to explain to help other users, is that in order to export your settings before uninstalling, you have to bring up the Options window and then go to each individual email account that's listed and click Export. I was not able to find that because the developer didn't give details. So I was not able to save my settings before uninstalling. But when I reinstalled it, it seemed to pick up some of my earlier settings anyway. I reconfigured everything manually just in case, and now I'm up and running again. (BTW, if nothing else works to find the Options window, you can go to your Firefox Add-ons and find X-Notifier and click on the Options icon. That was the only way I was able to do it because the X-Notifier toolbar was not working before I uninstalled the add-on.)