The Solar Neutron Activator does not accept Lithium via Gas tubes from the front side.
Instead it uses the Lithium, but doesnt turn it into Tritium.
(using forge 11.14.3.1446)

You need to input lithium through the bottom - tritium will come out the front.

My solar neutron activator don't work. I input the lithium to the bottom and I extract the tritium at the front but my lithium don't want to go in the solar neutron activator

yeah, bottom no longer works. Solar Neutron Activator is deleting the lithium on contact, and no other side but the one with the square will accept anything. This used to be a great mod. Apparently its gone into the garbage.

every pipe from mekanism acts like that

You can't connect mechanical pipes (fluid) to the solar neutron activator... as it only deals with gases (pressurized tubes)