Why won't this sketch solve?

[i-make-robots]

https://a360.co/3x83B8w

I'm building a model of some outward facing GT2 timing belt.  I used equations that use the number of teeth and the pitch to calculate the circumference and diameter.  Everything is then built on top of that.  I expected that I should be able to change the number of teeth and everything would update painlessly.  What I don't understand is why it refuses to solve.  Unfortunately the message is so generic as to give no hint.

I have tried removing the diameter dimension, after which I can manually resize the design.  If I re-apply the dimension, the sketch stays where it is and I get a failure message.  So the mystery deepens - if I'm allowed to do it, why won't the app set the diameter to my calculated value?

[jhackney1972]

You model link does not have the ability to download.  Please attach it to your Forum post. 

If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.