@Fabiorf
Yes OP must maintain his condition of nomination while his PR is processing. So if he had got approved by OINP by providing a job offer then he must still have the job offer until the day he lands as PR.
Well to my personal experience, my brother had the same situation as OP, PNP gave him 45 days to find a new job offer and update his PNP nomination. He had already got his work permit for the current employer approved recently but he was let go at the job. Meaning he cannot work for any employer since his work permit was closed.
He told PNP and they said back to him since he got PNP based on a job offer, he must find a new job offer in 45 days before PNP will notify IRCC and cancel his PR application. So my brother found a new job offer within the 45 days and updated PNP and PNP gave him a new PNP certificate with work permit support letter