Hi,
The default for start_position is end so it will only ingest entries that are written after LogStash found the file for the first time. Are you sure there were log entries written after that? Have you tried setting the log.level(logstash.yml | Logstash Reference [8.11] | Elastic) to debug or trace to find more information why the files are not read?
This should not happen - did you delete the sincedb file? The start_position is only used when detecting a new file. After that, the current position is stored in the sincedb file.
Best regards
Wolfram