Recently, Enfocus had warned PitStop users on Mac about updating to the latest version of Acrobat Update September 2021, which Adobe recently released.
The Mac version of this update caused an issue for PitStop Pro: when one or more objects are selected in PitStop Pro, the selected objects and anchor points are not displayed. Enfocus has published a knowledgebase article about this.
In the meantime, Enfocus has been able to fix the problem. You have to install the latest version of PitStop Pro (2021.0.3).
A reader of PDF-AKTUELL already reported this problem with PitStop in a german comment two days before the Enfocus warning and he also reported another problem with Callas pdfToolbox.
Windows users are not affected by this problem.