Accepting the premise of your question, I don't think there's a specific term for when someone attempts to create or point out irony but actually fails to produce an incongruity. If there were, then it would be widely used for the Alanis Morissette song Ironic[*]. The direct opposite of irony in speech is "sincerity", the direct opposite of irony in a situation is "congruity" and synonyms "appropriateness", "harmony". Or "fitting", "apt", "expected", "condign". None of these on its own emphasises a failure to be ironic, but you could say, "that's not ironic, it's totally appropriate".
This example most definitely is irony. Some forms of irony require intent, such as sarcasm[**]. This is a fairly weak situational irony, which does not require any intent to be ironic.
Since it was not deliberate, it is also unintended irony.
Either description would be appropriate here. Call it "situational irony" as an analysis of why it's ironic. Call it "unintended irony" to highlight the haplessness of whoever put the camera up in that position.
The reason it's a fairly weak situational irony is that all we have here is two incongruous elements (honoring Orwell while conducting surveillance), and the idea that the presence of the the plaque should give someone thought not to create that incongruity by placing the camera. A stronger situational irony would be if the plaque somehow caused the camera's presence. It's not usually the case with blue plaques, but imagine that this house has been turned into an Orwell Museum, and the camera is there because of attempts to steal a valuable final manuscript of 1984. Or even stronger, imagine that the government, in homage to Orwell, has chosen to install offices in the building with his plaque on it, and the camera is there to inspect the public as they come and go from the offices ;-)
[*] although one can argue that Ironic must in fact be ironic. Some of the examples given can just about be argued ironic (e.g. "a no smoking sign on your cigarette break": it would be faintly ironic to be granted a formal break for the purposes of smoking by someone who then turns around and plasters no-smoking signs everywhere). However you argue it, though, the song either ironically contains no genuine examples of irony or else ironically fails to achieve even that irony. In short, if you look hard enough for irony you can generally find some.
[**] albeit not necessarily pre-meditated intent. If you're sincere but your words sound like sarcasm, they actually are not sarcasm. If you want to be sincere but at the last minute choose sarcasm out of a sense of perversity, you have intent but not pre-meditated intent. At least, that's what you'd tell the judge.