Dimensions not showing on sketch

[ejb.roboguy]

Hey all, 

Total new guy to fusion here, just got an issue with dimensions not showing in sketch view. 
If I've got this totally the wrong way round, sorry for any inconvenience lol. 

The main issue is shown in the screenshot, opening a sketch I have created, ie editing, only shows one dimension of the sketch automatically. 
Using the sketch dimension button in the create tab I can show the dimension on another part of the sketch manually. 

I have show dimensions enabled in the sketch palette, so i don't quite understand why this is happening to even the simplest sketch (a cube, in this case)

[hamid.sh.]

I guess you haven't dimensioned the horizontal line or you have deleted it. That's why the line is blue (i.e. not constrained). Keep in mind in Fusion dimensions are not just sizes but constrains.

If you are new to parametric modeling and Fusion I suggest starting with Self-Paced Learning (accessible from Help > Learning and Documentation) before stepping into actual modeling.

[ejb.roboguy]

I wouldn't even know how to dimensionise it! Although accidental deletion is within the realm of possibility.  
After creating a new sketch on a separate project entirely it seems to be working as expected, very strange. I created the same sketch, a simple '2-point rectangle' square. 
Thanks for the advice on the self-paced work, I'll definitely check it out.