Tape Measure on Mac

Hi, guys, I’m new to this forum and Sketchup.
I’m having trouble resizing my drawing with the tape measure tool,
Here’s what I do
Click start point to measure
Click end point (line disappears)
Enter dims required (i.e.,; 3000mm) in box at bottom
Press return
Nothing happens

Am I missing something?
Is it a mac thing? (Im using the new macbook air)

It’s not a Mac thing, so you are likely missing some detail.

Most likely you need to switch the Tape tool to measurement mode instead of “add guide” mode. Press the alt/option key. In add guide mode (default) you will see a little plus next to the cursor. The tool needs to be in measurement mode for resize to work.

Thanks so much, Sorted