WebApp Tabs for Thunderbird Install Issue

Add-ons Add-on Support
#1

When tried to install WebApp Tabs 2.1.1-let-fixed on Thunderbird 38.5.0 I got a red bar with a message I never saw before in any Mozilla product.

The add-on from addons.mozilla.org could not be installed because it does not match the add-on Thunderbird expected.

Any ideas on what is wrong?

#2

This issue is being tacked at https://github.com/mozilla/olympia/issues/1111.

#3

Okay, so how do I get this addon installed?

#4

You can find the add-on on addons.mozilla.org, right click on the install button and choose Save Link As. Once you have the file, you just need to drag it to the Add-ons Manager in Thunderbird to install it.