Hello Kk4fpk,
We're sorry for the trouble you had, please reboot the machine once and then try opening few PDF files in Adobe Reader from Window -> Cascade -> Tile and see if that brings up the PDFs.
Are you not able to view all the PDF files or is it specific to one PDF file?
You may also refer and try the suggestion from the help article Can't open PDF
Please navigate to Adobe Reader's Preferences from Edit>Preferences>Security(Enhanced)>and disable 'Enable Protected Mode at startup' and 'Enable Enhanced Security'>Click OK>restart the application and check.
Note: Disabling Protected Mode and Enhanced Security is only for testing purpose, please enable it back.
You mentioned that you reinstall Adobe Reader twice, did you use Acrobat Cleaner tool to uninstall Adobe Reader? If not, please use Acrobat cleaner tool once to remove Adobe Reader Download Adobe Reader and Acrobat Cleaner Tool - Adobe Labs
Reboot the machine and install Adobe Reader from Adobe - Adobe Acrobat Reader DC Distribution
Let us know how it goes and share your observation.
Thanks,
Anand Sri.