Which symptom indicates that Order Type and Document Type field could not display Keys on the PO or PR screen?
On the Purchase Order screen, the Order Type field could not show Keys. Or on the Purchase Requisition screen, the Document Type field could not display Keys. For example:
On T-code ME21N, options like "Standard PO" (description only) are displayed by the system for the Order Type field, however, in the drop down list the keys are not displayed e.g. "NB". If there are many order types with same description like "Standard PO", then this may cause a problem as user does not know which order type should be selected.
Read more about Difference between the transactions ME25 and ME21N
You are getting this issue because of layout settings.
1. Click the Customize Local Layout (Alt+F12) icon On your session screen, for example T-code ME21N.
2. Select Options on the dropdown list.
3. Select Interaction Design > Visualization 1 > Controls area, tick the 'Show keys within dropdown lists' indicator
4.Then, go to ME21N again