You have the right to convert your bankruptcy case from Chapter 13 to Chapter 7 at any time. However, in order to convert your case, you must qualify for a Chapter 7 bankruptcy by satisfying the Chapter 7 means test. But why convert from Chapter 13 to Chapter 7?
The most common reason to convert is that you cannot meet the obligations of your Chapter 13 repayment plan (likely due to changed circumstances). It is possible that you lost your job, missed a few payments, and creditors lifted the stay, or you decided that your assets were not worth preserving. Or perhaps you suffering from an illness that has created medical debt that you can't pay. Maybe your household size has changed and the increased expenses make it impossible for you to make your Chapter 13 payments.
Whatever the reason may be, if you find yourself having trouble keeping up with your Chapter 13 repayment plan, you should consult an attorney to determine whether converting to Chapter 7 would be beneficial to you.