Reviving this dead thread as I finally have some answers. Some time back I faced the same issue. As soon as I got the notification to accept the 600 points from Ontario, my IRCC profile became ineligible, and I was not able to do anything. Unfortunately, in the letter that they send, they mention a list of reasons why that may be the case, but they do not tell you the exact reason. After some trial and error, I figured out that there was an issue with Proof of Funds for me.
There was a change in the minimum funds required, and I missed to update that in my IRCC profile. Once your profile become ineligible, there is no way to edit or modify anything. Your only option is to create a new profile, and that's what I did. I was confused how to communicate that to OINP folks but in a day or two, I got an email from Ontario asking me about the same issue with my IRCC profile. In the same email, they asked the following details:
1. The IRCC letter indicating that your old Express Entry profile was cancelled or became ineligible;
2. The Express Entry number/job seeker validation code for your new profile AND a copy of the letter you received from IRCC acknowledging the new profile;
3. A letter explaining why you updated your profile and a list of the additional or updated information you provided in your new Express Entry profile; and
4. Any additional information or documentation that is relevant to demonstrating your registration in the Express Entry system.
In my case, I got an up to date balance confirmation letter from the bank and added that for point number 4.
You have 72 hours to respond to that email. After providing them these details, within a week I got another nomination in my new profile and I was able to accept the 600 points. Hope this helps someone.