In our case it was the issue that the file format wasn't whitelisted on
the actual mid-sourcing server. the issue was resolved after TechOps
team of Adobe whitelisted it on their end.
Delivery and tracking logs are only stored for 6 months by default. If
you want to extend the length these are retained, you'd need to speak to
your CSM & TechOps to try and get this extended.
This would need to be done using the Enrichment activity. You can
configure it to accept data from two sources, and choose which is the
primary source. You then enrich that data with data from the alternative
source.