Processing on Q-clearance app terminated due to "(in)sufficient information"

I was somewhat shocked to receive a letter from today DoE stating that "processing for Q… "… was “administratively terminated”.
The supporting ‘evidence’ was simply that “sufficient information about… background” couldn’t be obtained during the authorization process (I guess, background checking).
No further information, or context, on exactly what was missing was provided. In addition, they didn’t ask me to include any further information.
I took a while filling out my eQIP and was very complete. I completed several years of schooling abroad and listed all schools and significant contacts from these years on the app.
They do mention on the letter an appeals process (you can write a letter) but without context I feel this would be exceedingly difficult to write- so it seems I am in a bit of a double bind.
Thank you in advance for any possible assistance.

This is merely speculation on my part. I am not on the adjudicative side of clearances. You may not have any sources to interview to get background information. You mentioned that you spent several years outside of the country. Do you have any sources that are now stateside? The best case scenario is someone that attended school with you abroad that is now in the US. The background investigation covers a particular window of time. If you were not stateside during that time, there may not be anyway for sources to be interviewed. I have seen subject interviews done abroad in certain countries. I have not seen sources interviewed in foreign countries where the subject is no longer present. Again, this is not factual information; just speculation.

Thanks for replying northstar. The vast majority of my foreign contacts (all except 1-2) are still abroad, yes. I have US citizens who can verify my time independently abroad who were there with me, and some of them were also listed in my application. However, it may not have been obvious which years and times they could confirm, and maybe there were gaps, especially if the interviews were not all done or well done well. I can definitely try to clarify and build a better timeline here , but I feel like in this case I’m taking the fall for an investigator who didn’t complete his/her job; and it doesn’t feel good. It also seems really strange I wasn’t asked for clarification. I asked a few folks who have been through this, and no one has seen an early termination on quite such vague grounds.