Dimention, No Entity Selected!

Hi all

I have made this drawing of a house I am planing to build, now I want to put in a few measurements but I can't get it to work. I follow these steps.

1. move in to the Dimentions menu
2. select lets say Horizontal
3. select one corner of my drawing (base fundament to say something)
4. select opposit corner
5. draw out the line wher the measurement shuld be.

Now I get this No Entity Selected in the command window.

So I try to dra a new object anywhere in the drawing area, a rectangle and repeat the above 1-5 steps, still no entity selected.

So I open a completely new window, draw the rectangel again and do the dimentioning stuff, now it is working....

What may be wrong. I have multiple layers in my house drawing, I have tried to merge all layers to one but still no success.

Ok, seems I found the issue my self.

I had the dimentions properties set up with default font size of 2.5 mm, and the arrows at a similar size. Having the drawing made in full size a wall with length 7,2 meters simply made the font impossible to see due to the zoom.