Did you convert a polyline to the alignment?
If so, then if your polyline lines were not perfectly tangential to your curves then Civil 3D creates unconstrained lines and curves in the alignment when converting the polyline.
In the image below I converted 2 polylines. The top one was completely tangential and as a result you can see the grip for changing the curve radius. The bottom one I purposefully moved the line on the left to break tangency and you can see that the grip is not available to change the curve radius.
If you want to "fix" this you can edit the alignment geometry and change the curve type "Constrained on Both Sides (Free)". This will "fillet" the two lines and alter the curve to make it perfectly tangential. See images below.
Alignment before fix:
Alignment after fix:
I had a closer look at you image and it looks like you are using a spiral-curve-spiral (I thought it was a normal fillet at first).
I am not that familiar with spiral-curve-spiral, but I think you can only change the radius through the alignment entities table. I could be wrong though, prehaps someone else with more experience with spiral-curve-spiral can assist.
You are obsalutely right.
But I dont understand what is reason and is it possible to solve this difficulty
Thank you for your respond.
It is not polyline in my case. I just imported alignment from InRoads SS2 as *.XML file
And I'm sure curves are obsalutely tangential.
As @Kyle-L mentioned below maybe difficulty is that, because I use spiral curve spiral?
Look at below screens. The curve without spirals are ok. But the curves with spirals looks that way.
Unfortunately, looking at the documentation, it looks like that is just the way it is.
https://help.autodesk.com/view/CIV3D/2022/ENU/?guid=GUID-BCA4F73E-4DEF-4F72-9DD6-91043FF10BBB
Here is the quote from the help:
"You cannot grip edit the spiral-curve-spiral curve group, but you can edit the entities to which the SCS group is attached. Make edits to the spiral or curve parameters in the Alignment Layout Parameters window or the Alignment Entities vista."