You may have overlooked the stage of this query . . . the OP already has an explanation being reviewed:
Some further observations:
For the OP, @tyatca, the overriding Program Delivery Instruction about what could happen can be seen here
https://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/canadian-citizenship/admininistration/general-file-processing/procedure-abandonment.html
Unfortunately the PDI is more complicated than it should be (and I cannot much figure out how to apply it to your situation) . . . it appears intended to cover a broad range of no-shows or no-responses, and in particular appears to be more strict than some actual policies or practices. That said, it is NOT easy to keep up with what the precise policy or practice is in regards to some particular steps in the process. For example, last I was aware, the PRACTICE in regards to a failure to appear for a test/interview event was to automatically reschedule it. This PDI suggests otherwise. I do not know the actual current policy or practice.
Moreover, IRCC does not make it easy to find some of the applicable policies or practices. In the past there was a PDI or Operational Bulletin (my vague recall is it was the latter, but I can no longer find it to confirm what it was) which at least somewhat described what constituted an "acceptable explanation," and explicitly stated that the failure to appear due to being abroad for an extended period of time WAS
NOT AN ACCEPTABLE EXPLANATION. I do NOT KNOW if there is still such a policy or practice, or even if there is one, how that is interpreted and applied. To the extent that was the policy, my vague recall is that it applied to no-shows for the ceremony rather than other events. But without being able to revisit it, I do not recall its details with any degree of confidence. (I may have a copy on a hard drive somewhere in the labyrinth of data stored on my network, but I could not put my cursor on it this morning.)
I believe they are fairly liberal or even lenient in evaluating the reasonableness, the acceptability, of proffered explanations . . . and especially so when the applicant contacted IRCC about rescheduling the event BEFORE it, rather than after having missed it.
IN THE PAST (again, I am fuzzy on current policies and practices) CIC/IRCC was more strict in regards to missing a scheduled citizenship ceremony than other events.
I wish I could be more helpful. I can offer this:
generally it appears that IRCC is fairly liberal if not lenient so long as the applicant is qualified and remains actively engaged in pursuing the application for citizenship . . . there is a clear preference to determine the outcome of the application based on its substantive merits and NOT on procedural technicalities. So there probably is no reason to worry much . . . that "probably," however, is based on my sense of how these things go more than what the policy or practice actually is, since, again, I am NOT sure what the current policy or practice is.
Further response to this post:
I am aware that many participants here do not make fine distinctions based on precise terms. My guess is that by "rule" you are referring to either policy or practice.
The actual rule is otherwise. The rule is specified by statute, by Section 13.2 in the Citizenship Act, which is quoted in full in the PDI I linked above. In pertinent part, which is Section 13.2(1)(b) to be precise, it states:
"The Minister may treat an application as abandoned . . . in the case of an applicant who must take the oath of citizenship to become a citizen, if the applicant fails, without reasonable excuse, to appear and take the oath at the time and at the place—or at the time and by the means—specified in an invitation from the Minister."
What matters, however, is the current IRCC policy and practice, the way in which it actually applies this "rule."
As I noted above, I do not have a clear view or understanding of the CURRENT actual policy and practice. It is my impression that as regards the failure to show
for a test/interview, what you describe is the practice . . . BUT to be clear, I am not sure of this. It has long been the practice to automatically reschedule no-shows for a FIRST scheduled test. IT HAS BEEN OTHERWISE for oath ceremony no-shows.
In any event, the OP is past that stage, and apparently at the stage where the explanation for a no-show (or request for rescheduling . . . this is not clear from the OP's posts) is being reviewed to determine if it is acceptable.