Why is my tech nonexistent when all my Sims are educated?

At first, I got level 3 tech but suddenly my tech level became 0. I didn't change anything, I have one university and three colleges. Almost all of my Sims are educated.

Why did this happen?

This tech falling also happened several times in my another city. All my industrial sector is shouting about lack of educated employees.

Is this a bug or something I have done wrong?

Here are some screenshots:

The "educated workers" message is misleading. It is only about tech points, not about workers.

An explanation of the tech points system.

Your tech point demand is too high. The tech point consumers are burning up all the tech points such that none accumulate.

Reduce nuclear power, electronics specialization, industry in that order until tech starts accumulating. You'll be able to see this in the tech dataview (the right dataview button in your screenshot).

If you happen to also have highschools or gradeschools, remove those. They do not generate tech points. They keep students from going to schools which would generate tech points.