Please ensure your copy of Acrobat is updated, to check for any pending updates, launch Acrobat > Help > Check For Updates.

If you are still experiencing the issue, help us with the following details:

1. Acrobat version installed:  https://adobe.ly/3PQQ7nE
2. OS name and version.
3. Screen recording showing the problem. 

The above details will help us reproduce the issue on our end, precisely replicating the workflow. 

Additionally, here are a few things to try:

1. Right-click the comment and choose “Properties” — check if the “Locked” box is selected. If so, uncheck it and click “Make Properties Default” so future comments aren’t locked automatically.
2. Check the document’s security settings under File > Properties > Security. If the PDF is signed or certified, Acrobat may automatically lock any changes — including comments — to preserve document integrity.
3. If the issue occurs in all PDFs (not just one), it’s possible that a preference or profile is corrupted. If needed, we can walk you through resetting Acrobat preferences: https://community.adobe.com/t5/acrobat-discussions/how-to-reset-acrobat-preference-settings-to-default/td-p/4792082 

Let us know what you find — happy to help further based on that!

Best regards,
Tariq | Adobe Community Team