@MotherOfDragonite
VanGoghsDog You said "I have no idea what you've been reading bit of course you tell employers if you have gaps in your skills due to being off for a whole year."
And I said, in response to that, that no, there is no obligation whatsoever to disclose absences from work for sick leave or for maternity leave.
So, as you have confirmed, I did not say it was an obligation.
I am at a loss as to how one could go through an interview, discuss one's experiences, within that rely on the specific and very necessary experience in one particular job that you never did, and fail to say you were not actually at work during that job so quite simply do not have that experience.
So, if that is what the OP did, she lied. She either lied outright when asked questions, or she lied by omission. And the employer is perfectly entitled to pull the offer on those grounds and on the grounds of lack of experience and on the grounds of lack of reference.
None of that is anything to do with her pregnancy related ill health (and, remember, we have no idea what the ex employer actually wrote on the reference, putting under "experience" that the OP was off is not disclosing medical records) nor to do with her maternity leave.
ACAS are great, by the way, but they are understaffed and, fundamentally, not always right. I have had them advise employees who have then gone on to bring a tribunal which they have then lost where it was blindingly obvious they would lose. This happens regularly. They literally always advise people to bring claims if mediation fails (and for 'mediation' read 'getting the employer to pay out even if they are in the right').
I have gone through no end of rounds of mediation with them and they never mediate in favour of the employer - they are an employee advocate, which is great and really useful, but they are not always realistic about the actual law.