Research not available.

The issue
After research some issues, the Cargo Depot, Advanced Diesel an all what is dependend on those, cannot be researched, hence no rubber, no weapons, and so on.

Attachments
This is a screenshot of the researche tree.

You need to discover an oil rig on the world map before these get available.

Yeah, I noticed already. Was not realy clear. Maybe you make a better remark in the techtree or something. But great game so far.