Problem with engineer (and we need one)

Played ET after a long time few days back. I already then had a problem, but I thought I didn't remember the buttons. Now I started my own server without anyone else, and I just can't use F to build anything. I tried to change my F to T but still as an engineer I can't build anything. Funny thing is, that I can use F to shoot map weapons, just can't build them. Any advice?
Edit. I tried with the official servers which were opened just a while ago, and yet a same result. I can you tank with F, I can use machine gun if it's build with F, but as an engineer, I can't build anything.

You might of figured it out already but you need to pull out the pliers first then hold left mouse button

You might of figured it out already but you need to pull out the pliers first then hold left mouse button
Thank you so much! I seriously couldn't remember that!