I found the error.
I have missed to define i2C address!
after this line:
u8g2.setI2CAddress(0x3F * 2);
everything works.
By the way....this constructor works also:
U8G2_ST7567_ENH_DG128064I_F_SW_I2C u8g2(U8G2_R0, SCL, SDA, U8X8_PIN_NONE);
a little confusing is that all example codes have no definition for i2c address.