I have had issues in the 2026 version of illustrator. The smart guides disappear when I choose the eyedropper tool.
After many hours of support with adobe, they found out it was a change that was introduced to the 2026 version, to improve overall application funtionality.
However my feedback to this, is shared with their engineering team, and they will further review this behavior.

My hope is that they discard this new change, as the smart guides can be turned off totally, if you do not wish to use them, so I do not understand, why it should disappear on some tools. Working the 2026 version, I now have to activate the smart guides every time I use the eye dropper tool, (which is very often), and then again when choosing another tool, because the smart guides does not active automatically when switching back to a tool, that from the beginning was activated with smart guides. So I have to activate the smart guides all the time now...