I upgraded the logstash version from 7.12.1 to 7.15.1 and I'm not seeing logs in Kibana from the source host I'm testing with. Is this too much of a jump in versions or did something change in 7.15.1 that I need to update on the logstash server?
Did you install any third party or additional addons/filters/inputs/outputs?
If you did you have to reinstall them with the newest version.
Check the logstash logs to see what's going on.