Hope you are doing well and sorry for the trouble. As described the application doesn't recognize text.
What happens when you try to run the OCR, do you get any error message? If yes, please share the screen shot of the error message for a better understanding.
Is this a behavior with a particular PDF file or with all the PDFs? Please try with a different PDF file and check.
Are you on Mac or Windows machine and what is the version of the OS and the application you are using? To check the version go to Help > About Acrobat and make sure you have the latest version installed. Go to Help > Check for updates and reboot the computer.