On Firefox 43 and later you need to set `xpinstall.signatures.required` to `false` via `about:config`.
For Firefox 46 and later, you'll have to try an unbranded Firefox (including Beta, Aurora, and Nightly) to try development builds because the option will be removed on official Firefox 46 and later.
You can start Firefox with temporary clean profile by a command line `-profile`, like: `"C:\Program Filex (x86)\Mozilla Firefox\firefox.exe" -no-remote -profile "%Temp%\FirefoxTemporaryProfile"`
Then, please report the bug with these information:
## Feature requests can be tagged as "out of purpose"
Please see [the readme page](./README.md) before you post a new feature request.
Even if a requested feature is very useful, it is possibly rejected by the project policy.
Instead, please tell me other addon which provide the feature and report a new issue as "compatibility issue with the addon, TST should work together with it".
## Translations, pull requests
If you've fixed a problem you met by your hand, then please send the difference as a pull request.
And, if you translated TST for your language, please feedback it for me as a pull request.
You'll be able to do it without any local application - you can do it on the GitHub.