If you are on a monthly payment schedule, then the Bankruptcy and Insolvency Act (BIA) stipulates that you can miss or defer two payments during a consumer proposal. You should still contact your Licensed Insolvency Trustee to let them know you are having trouble.
However, if you miss three payments then your consumer proposal is automatically annulled. If you are on a non-monthly payment schedule, the proposal is annulled if a single payment is missed by more than three months.
All payments made to that point will still be credited to your accounts. However, you will not get a refund of any fees you paid. And if you wish to continue and complete the proposal, you will need to go through the process to have it reinstated.