I am using Windows XP .
What is UAC?
Knowing that you're using XP rules out UAC as a problem. Mouseover the first UAC for a brief explanation of the acronym.
Sometimes switching from the New UI to the V11 UI and then back to the New UI activates stubborn tools (Tools / UI Themes). I'll agree with Henry that the Chain Polyline is probably a Pro tool. Does the "T-Meet 2 Double Lines" tool show up in "Tools / Customize â€” Commands" under the "Modify / Other" category?
I don't have V12 Deluxe, so I'm not sure if these two tools are available or not.
Designer, Deluxe, (Professional, Expert, Basic), Platinum
Windows 10 Pro (1903), 64-bit