Hope you are doing well and sorry for the trouble.
Could you help me with few details asked below:
1. Have you tried to logout of the application, reboot the computer once and relogin with the same Adobe ID?
Would you mind sharing the version of the Acrobat Reader DC you are using? To check the version go to Help > About Acrobat and make sure you have the latest version 21.07.20095 (Win) , 21.07.20096 (Mac) installed. Go to Help > Check for updates.
Also try to logout of the application, reboot the computer once and relogin with the same Adobe ID and see if that works for you.
Also please collect the logs of the affected machine as described here - https://helpx.adobe.com/creative-cloud/kb/cc-log-collector.html and share the logs with us via document cloud - https://helpx.adobe.com/document-cloud/help/sharing-pdfs.html
Let us know how it works at your end. If you have any further queries please feel free to reach out to us.
Hello and thank you for the response.
1. The problem is in the free Adobe reader, so we do not sign in with an Adobe ID. Reader version is 2021.007.20099 (Version in the attachment).
2. This problem sometimes goes away when we do Help > Repair installation. After that the panels may work for a while, but eventually they go blank again.