Fortian, Thanks for the information. When you said material master instead of article master in an earlier response in this thread, i should have thought it should only be the core system.
What looks different to me is, again in your screenshot, the past periods are available for editing.
Can you let us know what are the planning horizon details you used while creating the planning type?
Like planning start, future and (the important one being) historical periods.
Just another check. Are you using different planning calendars and with differing start dates for your infostructure and plant? Ensure that sufficient periods exist.
It is also good to check if the base unit of measure in Info-structure is same as it is in material master.
Paste a screenshot of your info-structure planning parameters also for a check.
As we know the SOP aspects have not been changed at all over a long time, there are no new notes to look for and this looks more like a data/maintenance issue.