Hi
Adobe Acrobat and Reader official update (20.009.20063) containing this fix is now available. This update will be automatically pushed to all existing installations of Acrobat and Reader. You may also manually trigger the update early by opening the application and going to Help > Check for Updates.
More information about this release is here: https://helpx.adobe.com/acrobat/release-note/release-notes-acrobat-reader.html
In case comment app does not open by default for the first time, please follow the steps:
1. In Acrobat, go to Edit > Preferences (Windows), or Acrobat > Preferences (Mac).
2. Under Commenting, select the option – Show Comments Pane When A PDF With Comments Is Opened. Click OK.
Kindly try it out and let us know your feedback!
Thanks for your patience and support!
Regards,
Arvind