Extension no visible in LibreOffice writer. How to fix?

I installed the dmaths extension in libreoffice (5.1.4.2) but I can’t use the extension, it’s not visible from LO Writer.

Installed package:

But no toolbar option:

Have you read all of the installation instructions? Hint: You have to restart LO twice before you can use the extension.

@floris I have. still nothing …

Then contact the developers, you paid for it after all.

Lol, no I did’t it’s in the repos, I installed it via Synaptic …

That extension seems to be non-free software contrary to the declaration on the LO extension page. At least, they require a payment and provide no link to source. Thus, contact their support.

What are you talking about? The dmaths is licensed under the GPL.

I am talking about the fact that they require a payment of 10 to 35 euros if you want to download the extension (which is OK for the GPL) and they provide no link to download the source (which is in violation with the GPL). Thus, ask those people.