Strategy group has not been maintained

What causes this issue?

No valid requirements type could be determined.
This may be due to one of the following reasons:
No strategy group has been maintained in the material master record.
In the material master record, you have maintained an MRP group,
however, no strategy group has been allocated to this MRP group.
If you entered a strategy group or an MRP group in the material master
record for which a strategy group exists in Customizing, then the
system determines the requirements type from the strategy group in
Customizing and proposes the main strategy.
&HINWEIS&
The strategies or requirements types allowed for planning a material
are grouped together in Customizing for demand management in the
strategy group. This strategy group is allocated to the material in the
material master record, either directly or via the MRP group.

How to fix this error?

Check the possible causes of the error and maintain the correspnding
function:
Check whether an MRP group or a strategy group us entered in the
material master record.
<DS:TRAN.MM02>Proceed</>
Check in Customizing whether a strategy group has been allocated to the
MRP group.
<DS:TRAN.OPPU>Proceed</>

Error message extract from SAP system. Copyright SAP SE.