I am in the same situation. I have not worked with the employer before. However, my contract with the employer is still valid and I still have evidence showing the email correspondence I sent to the employer to resolve this issue. I called IRCC yesterday and narrated my situation and they sent me the guidance to apply for the Vulnerable Open work permit. I have reported to Service Canada and CICC and I am going to add this to my application. Also, with my case when I got the job offer from the immigration consultant, I sent it to the employer for verification. However, he failed to respond to my email and rather informed the immigration consultant about my out reach. I have this email correspondence to show as evidence. Also, I learnt that the more evidence you show the faster your application.