We are sorry for the trouble. As described you are not able to view the filled text in the PDF form
++ Adding to the discussion
Would you mind sharing the version of the Adobe Acrobat DC you are using? To check the version go to Help > About Adobe Acrobat and make sure you have the latest version 20.12.20043 installed. Go to Help > Check for Updates.
Is this a behavior with a particular PDF file or with all the PDFs? Please try with a different PDF file and check.
If the file is stored on a shared network/drive, please download the file to your computer locally and then try to open the PDF and check.
For testing purposes: Please try to turn off the protected mode and see if that makes any difference. Go to Edit > Preferences > Enhanced Security > Uncheck 'Enable protected mode at startup' Turn off the protected mode and uncheck the enhanced Security > Click OK and reboot the computer. Note: Turning off the security may possess security risks, please turn on the security after testing.
Also please try to open the PDF in a web browser (Chrome) for testing and see if the pdf file is displayed fine there.