It seems that the byebug gem is not successfully installed.
run 'bundle install ' to check the gem installation, if it goes well, it should list the gems that you have installed.
if there's byebug in the list, check the /var/canvas/vendor/bundle/ruby/3.1.0 ( depends on your installation path) to see if there's the byebug gem.
other wise, delete the vendor/bundle folder to re-install it again.
if you find the byebug gem there, but still not working, set a var in the apahce2 config file;
just follow the SetEnv RAILS_ENV production:
SetEnv GEM_PATH /var/canvas/vendor/bundle/ruby/3.1.0 <--- again, this path depends on your installation path.
Best,