You should primarily search for its installation folder and analyze its config.
If you have it installed properly, you should be able to run the cxommand "Logwatch" ath the SSH command line and if it is working, you'll see that in about 30-40 seconds the process ends and if the conf file is defining an email address to send reports, you should receive that report via mail.
If you receive the report, then check the daily crontab, run this:
if you see an item about "0logwatch", you can simply test the sanity of this link by simply "less 0logwatch" (you'll view the source code of Logwatch). Tell what is the version you have installed, look at one of the first lines of code that contains "my $Version =". 7.3.6 is the last version.
If you can run the executable and see the code thru the cron folder, you maybe need to check the configuration looking for the address to which it is sending reports (commonly: root). If, although, it used to work in the past, its cron probably was deleted from crontab by some reason.
At the SSH run:
find / -name logwatch.conf
You'll find the conf file that need to be opened and checked. Look for the "MailTo =" and check if the destination email is correct. Usually you'll find two locations for the logwatch.conf file, being what you need the one located at /etc/logwatch/conf/logwatch.conf
Be aware of old installations of Logwatch since they changed the locations for the common folders and I just did a mess when "upgrading" last month. If you want to reinstall/upgrade it's a good idea to delete all the actual files and do a clean install.