RE: planned purchase orders not linking to purchase agreement
In the Master planning parameters you can specify whether AX should try to find and link purchase agreements. Look at the parameter in master planning called find purchase agreements. The way this works is that when you have a planned purchase order that is suggested from master planning, then when it is firmed and the parameter is not enabled then the price is picked up from the default price of the item, so when you have purchase agreements they will be ignored.
When you enable the parameter, then master planning will check, whether there is an agreement for the item from the vendor that is the default vendor for the item and apply that to the purchase order when it is firmed.
When creating release orders against purchasing agreements with value commitments, you have to add item quantities in a different way -, see this quote by Microsoft:
“Only commitments of the Product quantity commitment type are available in the Create a new release order form. To create a purchase release order from commitments of the Product value commitment type, you must first create a purchase order, and then you can add purchase order lines for these items.”
— technet.microsoft.com/.../hh545520.aspx
However, if you have quantity commitment then this should not be the case so double check the specific agreement is set to quantity not value.
Do you have any min or max release parameters set?