Doc Library Won't Upload

Document Library won't accept file uploads. Opigno v2.11. I can create Folders just fine. Issue, specifically, is in the field for Files: selecting upload a file launches file explorer >> select/open a file >> file is not loaded (btw, no back, cancel, or return on this page so have to return to LP and refresh). The curser spins upon as if processing file, but no file gets loaded. Tried PDF and Doc files, and tried drag/drop. I'm sure I missed something simple somewhere... Help?