Hi Caetano,
I have a much similar problem.
In ME51N the button "BOM" is missing since some made configurations on MM-MRP. I even have an old PR created where I can see the button on one item but if I create a new item on that same requisition, for the same plant and material, the "BOM button" is still missing for this new item.
Do you please have any ideas on what else I could check?
Thanks a lot,
best regards,
Douglas