How to configure grabbing of xmltv file in Tvheadend on LE 12.2.1?

    I just upgraded Libreelec from a really old version to 12.2.1 (actually a new install on fresh SD card. I just installed whatever the SD-Card Creator was defaulting to). I am struggling to configure the grabbing of the xmltv file from my network file system. The file is accessible from the libreelec host. The dialog in the TVHeadend configuration screen where one would enter the file path is greyed out. I have searched with google trying to find solutions and am not finding something that is succeeding. I have tried entering the path as extra arguments on the Internal tv_grab_file entry within the TVHeadend configuration web interface.