I think they paused this in July.
"May I comment on reviews about my products and services?
As of July 10, 2025, the Reply to Review feature is paused.
The intended purpose of this feature is to address critical reviews and foster meaningful communication where it is most impactful. To ensure the feature is used as intended, the Reply to Review capability is paused while we re-evaluate this offering. At this time, there is no set date for when this feature may be reinstated. Please note that any Reply to Review submissions made will not be published."
https://gpivendorresources.gartner.com/en/articles/6812585-vendor-site-presence