To install do the following steps. 1. Unzip the files on the downloaded file. 2. edit file "install.rdf" in a text editor 3. search for "Thunderbird" comment line. 4. Just below comment line find "maxversion" line. I changed it to version "52.5.*". (My current version is v52.5.0 on linux.) 5. Then zip all the files to the same name it was previously. 6. Install addon. It worked for me.
Thanks for the email. I should have said it is on Thunderbird 45.5.1 that it shows "Not available for Thunderbird 45.5.1" It would be 5 stars if it can work again like it did on previous versions of Thunderbird. The strange thing is that I also have TB Portable version 45.5.1 on a stick, and it works perfectly well there... just won't install on the non-portable PC version.
I only started using Thunderbird recently and love it! Then I saw I can have an Afrikaans spell checker and was delighted as I am Afrikaans. But now I see that it is not available for the latest version and havent been updated in 3 years!!! Disappointed.
Thanks for answering. It says, when trying to add the Add-On to Thunderbird via the Add-On manager online that it is not compatible with TB 17.0.2. However, when I downloaded it and added it manually as an xpi file all went well and it appears to be working. Not sure why TB gave it a "non compatible" - but it did.