How do I investigate if my rules are being applied? I did not see alerts trigger as expected.
You can check for rule matches in the Data Explorer. Using a query similar to the following will return a list of rule IDs and the number of the times they have triggered an alert in the timeframe provided. The example below checks for AWS Cloudtrail rule matches.
SELECT p_rule_id, count(p_rule_id) FROM panther_rule_matches.public.aws_cloudtrail WHERE p_occurs_since('48 hours') GROUP BY p_rule_id