I have a current TS with the DoD from a previous summer internship and was looking for other opportunities for the coming summer. I was interviewing for both Agency C and this contractor and found out right before the interview with Agency C that I got my offer from the contractor. I tried to cancel my interview with them when I found out, but around a day later during the time my interview was scheduled, I got a bunch of communication from the agency asking if I was still showing up. I explained I had tried to contact them a day earlier, but I’m now wondering if that mishap will affect me when they process my SCI upgrade for the contractor internship. Am I overthinking this? 
Definetly overthinking. A no show to interview does not do anything. you have the right and some circumstances may not let you attend an interview.
Thats what I was thinking, just wanted to make sure I was in the clear. My only concern is that this is an IC agency that does their own clearances, and that they would deny suitability as kind of a f*** you 
Did that internship traumatize you? A no show at a federal interview should not have any bearing on a job at another place, especially with a contract company.