This is a completely different add-on from the original Morning Coffee, so it won't know about the sites you set up with the original. You'll have to set them up again. The best way to do that is with the tab context menu, as illustrated in the screenshots. Right-click on the tab for a site you want to add, select the "Add Tab to..." menu item at the bottom of the context menu, and select the day or days you want. Once you've done that, the button should work as you expect.

If this works for you, please consider revising your rating. If it doesn't, please send me an email and I will do my best to make it work. Thanks for trying it out!

Thanks for using Morning Coffee Quantum! Let me see if I can help with the issues you've mentioned.

You can probably get the icon back via Firefox's Customize feature. In the toolbar to the right of the location text box, look for an icon that looks like three horizontal lines. Click it, and you should get a menu that has a Customize option about halfway down. Click that, and you (hopefully) will see the Morning Coffee Quantum icon among all of the available icons. You can then drag and drop it back onto the toolbar.

Unfortunately, due to the way the new web extensions work, I couldn't set up a custom right-click on the button. But you can add sites to your daily lists another way - through the tab context menu. After you've opened a tab for a site you want to add, right-click its tab and select the "Add Tab to..." menu item in the menu that appears. Then you can pick your day(s) to which you want the site added.

Once you've added your sites, clicking the coffee cup icon should load them just like you remember. I hope this helps!
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In response to your additional question: the add-on doesn't have a "open your daily sites upon launching Firefox" feature yet. I might try adding one in the future, if there is enough interest and there exists the capability to do so. Currently, you have to click the button (or use the key shortcut) to open your daily sites. On the options page, there is an option to close all of your currently-open tabs, replacing them with your daily sites, when you click the button. That might get you something pretty close to what you want.

I've added an FAQ to my add-on homepage that addresses both of these questions, but to give a quick reply to both:

* There's currently a way to "manually" import/export (I give step-by-step instructions in the FAQ)
* Due to differences in the desktop and Android versions of Firefox, there probably won't be a version for Android.

Hope this helps! Thanks for using Morning Coffee Quantum, and for the kind words!