Get a really, really good lawyer that specializes in these types of cases. I'd suggest you're in for a tough fight.
-October 1/2023 to October 9/2024 is 375 days (1 year 8 days)
-you confirm being in a serious relationship (despite being refused in 2021 for common law) since 2019. The prior common law application will likely work against your argument you weren't common law when you made your landing.
-Unless she had a place of her own (different address, rent receipts, separate utilities, or a leasing agreement), based on historical applications and available information, IRCC has likely judged the situation correctly and the onus will be on you to prove otherwise.
I fully agree with Buletruck. You have been in a relationship (self-admitted) since 2019, and residing continuously together since December 2021. AND solely together in a separate place for over 12 months (Oct1, 23 to Oct x, 24) before becoming a PR. Unlike many, you clearly were AWARE of the common law possibility, since you submitted some kind of common law app in 2021 (no reasonable argument can be made that you were completely unaware - which is usually a losing argument anyway, AFAIK). Your counter about 'we did not live like common law partners' is weak - you were residing together, period.
Game over. There is no room for argumentation otherwise (IMO). Your partner should find ways to qualify for PR on their own.
And the case seems such a lock (against you) that you should be aware that chances of success in some kind of appeal / legal challenge are low and likely to be extremely costly and lengthy to even attempt to challenge.
[Editadd: you can (indeed must) of course respond to the PFL with whatever / best arguments and evidence you can muster, with or without legal assistance. In terms of high costs and long waits - I'm referring primarily to subsequent legal challenges, and I'm not an expert in the basic appeals process (probably simple appeal can be done without legal assistance but chances of success usually low.) Court challenges very expensive and lengthy.]
- Due to the prior refusal, we were cautious about claiming common-law partnership due to the non-conjugal nature of our housing arrangement, and were also recommended so by our RCIC on day of declaration. ... The household was non-conjugal: no joint lease, bank accounts, tax filings, or exclusive living space.
In my opinion, you misapprehend the nature of what 'non-conjugal' means here. Conjugal, at heart, means romantic/sexual. Other evidence (or lack of same) of joint household/shared expenses are
supportive of it being a true/serious conjugal relationship, but are not determinative (their absence makes it more difficult to demonstrate it
was conjugal, but the converse is not true - their absence certainly does not prove it was
not conjugal). The fact that it was a real relationship (conjugal) is shown already by your previous application - you can't on the one hand apply for common law and then argue years later it wasn't a real relationship.*
Now you say your RCIC provided this advice - that is (IMO) a deeply shocking oversight and close to complete incompetence, and this consultant should be reported / you must complain. I doubt this will provide much comfort to you.
You should of course see a lawyer and to the extent there is a legal case to be made, perhaps the lawyer can find a leg based on this poor counsel - or get your money back / some compensation for this gross incompetence. (My guess is that this will be difficult, too - legal limitations in contract or lack of evidence).
Good luck though. Although I think this case is cut and dry, I think the (effective) lifetime ban on sponsoring is overly harsh. But it appears to be the current stance taken by IRCC.
* The 'law' about conjugal / common law and etc is considerably more complex than me boiling it down (and as far as I can tell, hampered by difficulties of evidence, e.g. proof of sex/'romance', and no firm requirement/definition of either that can be relied upon), and it depends on context (among other things, IRCC's statutes and regs about what they recognise as 'common law' are not identical to those in common law/in the provinces, and since it's their own definition, it's not even 'common law' per se). That said, I'm not here to have a legal argument and I am not a lawyer. The point is, I don't think those finer, abstruse points of law/common law etc are likely to be argued here - your case seems quite cut and dry, to me, and I would be apprehensive that you could waste a lot of money arguing the finer points (unsuccessfully).