I'm told that this a plugin problem, and was also told the Kobo Ultilities forum was the place to go for help this issue, so hopefully this is the right place...
calibre, version 4.21.0
ERROR: Unhandled exception: <b>NoSectionError</b>:No section: 'Reading'
calibre 4.21 embedded-python: True is64bit: True
Darwin-18.7.0-x86_64-i386-64bit Darwin ('64bit', '')
('Darwin', '18.7.0', 'Darwin Kernel Version 18.7.0: Thu Jun 18 20:50:10 PDT 2020; root:xnu-4903.278.43~1/RELEASE_X86_64')
Python 2.7.16
OSX: ('10.14.6', ('', '', ''), 'x86_64')
Interface language: None
Successfully initialized third party plugins: Gather KFX-ZIP (from KFX Input) (1, 33, 0) && DeDRM (6, 7, 0) && Package KFX (from KFX Input) (1, 33, 0) && Kobo Utilities (2, 11, 0) && EpubSplit (2, 9, 0) && KFX metadata reader (from KFX Input) (1, 33, 0) && KFX Input (1, 33, 0) && Barnes & Noble (1, 2, 15) && KePub Output (3, 2, 13) && KePub Input (3, 2, 10) && EpubMerge (2, 9, 0) && KePub Metadata Reader (3, 2, 9) && Fantastic Fiction Adults (1, 1, 0) && Find Duplicates (1, 7, 2) && Fantastic Fiction (1, 3, 0) && Kobo Books (1, 8, 0) && KePub Metadata Writer (3, 2, 12) && Count Pages (1, 10, 0) && Goodreads (1, 4, 0) && Obok DeDRM (6, 7, 0)
Traceback (most recent call last):
File "calibre_plugins.koboutilities.action", line 832, in set_reader_fonts
File "calibre_plugins.koboutilities.action", line 4714, in _update_config_reader_settings
File "lib/python2.7/ConfigParser.py", line 753, in set
File "lib/python2.7/ConfigParser.py", line 396, in set
NoSectionError: No section: 'Reading'
Failed to set Reader Font on a Kobo Libra H2O
Error Log cannot attached be attached as apparently the limit is 1 MB and the file is 2.07 MB. If it's needed, you can find it here
https://bugs.launchpad.net/calibre/+bug/1888038