Drop-down Menu keeps hiding and when I click on a open tab it open is its own window.

Hi Lans

Hope you are doing well and sorry for the trouble. As described, drop-down Menu keeps hiding and when you click on a open tab it open is its own window.

Would you mind sharing the workflow/steps you are doing to open the tab, a small video depicting the issue would help us to better understand the issue.

What is the version of the Adobe Acrobat Reader DC you are using? To check the version go to Help > About Acrobat and make sure you have the application updated to version 21.05.20048. Go to Help > Check for updates and reboot the computer once.

You may also try to check/uncheck the option to open documents in same window and see if that helps. Go to Edit  (Win), Adobe Acrobat (Mac) > Preferences > General > Open documents as new tab in same Window. 

You may also try to reset the Acrobat preferences to default as described in the help page https://community.adobe.com/t5/acrobat/how-to-reset-acrobat-preference-settings-to-default/td-p/4792082

Regards

Amal