I can not enter a roundabout

Hi all.
I entered a roundabout, but I can not use the tool to make perfectly circular the layout of the road.
I selected the roundabout which I entered, but the tool is disabled.
What’s wrong?

Hi There,
OPTIONS in the top right corner. TICK show toolbox. A tool box appears. Click OK. (You can hold and drag the toolbox where you want it.) If the circular feature is not showing on a bottom row then click SHOW MORE.
Highlight/select your roundabout then click the MAKE CIRCULAR feature in the toolbox.
Your way/roundabout must be joined up (a complete circle) for the feature to be activated.
Hope that helps.
Regards Bernard

Thanks for your reply.
What you said is exactly what I had already done.
But the MAKE CIRCULAR feature is DISABLED.

Is it this one here :


There are several problems with this roundabout and the ways leading to it.
I’ll send you a PM

Kind regards