I’m looking at a similar timeline: Job offer in June 2018, paperwork submitted July 2018, interviewed March 2019, been waiting for a poly ever since. This is for a TS/SCI for a private contractor, so I don’t even know which agency is conducting this - my HR person simply refers to them as “the customer” and tells me I’m still processing. I reached out to my senator and am hoping to get some answers but I’m not hopeful.
Before I got this job offer, I was waiting on a Secret clearance with the DoD since March 2017 that also was never completed. So overall I’ve had two back-to-back investigations that have each gone on for 400+ days each, with no clearance granted in either.
EDIT: change December 2018 to July 2018, this was a mistype.