You can still build roads, but the system now considers the compactness/density of the overall shape. You’ll need to fill in around the roads with more plots, until the compactness score on that road beacon increases to a “good” %. If you look at the beacon, you should be able to see the compactness score in the details.
I think you may want to take a step back before looking into that.
If it was not that beacon that lost the prestige, then you could be running in circles
Periodically, I would take a snapshot of your total Settlement Prestige, with all the beacon’s prestige amounts shown.
That way, if it happens again, you will know which beacon lost a chunk of prestige, and will know which one to focus on.
With “larger” builds that have many beacons, sometimes running around trying to find 1 specific spot is a very hard way to go about finding the root of the problem. This way, you’ll know which beacon is the issue =D
If you plot up or down in that corner spot I think it will turn blue.
However, I think the fact that it’s blue and not green means it’s a road, or not compact, or both?