Activity type & is not allowed for business transaction &

What causes this issue?

In business transaction &V2& you entered activity type &V1&, category
&V3&. This category is <LS>not</> allowed in business transaction &V2&.

System Response

You can use only activity types of given categories in a given business
transaction.
The following activity type categories are valid for a given business
transaction:

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

<ZH>RKL</> (Direct Activity Allocation):
Category 1 (manual entry, manual allocation)
<ZH>RKN</>, <ZH>RKIL</> (Indirect Activity Allocation):
Category 3 (manual entry, indirect allocation)
Category 4 (manual entry, no allocation)
<ZH>RKLT</> (Template Allocation Actual):
Category 1 (manual entry, manual allocation)
Category 2 (indirect calculation, indirect allocation)
<ZH>RKPS</> (Template Allocation Plan):
Category 1 (manual entry, manual allocation)
Category 2 (indirect calculation, indirect allocation)
<ZH>Note</>
You can post category 2 (indirect calculation, indirect allocation) and
category 5 (calculation and allocation using target=actual activity
allocation) activity types
<ZH>manually</> only if the indicator <LS>Manual actual quantity</> is
set in the activity type master data.
If this indicator is set for an activity type of category 1, 2 or 5,
you can post the activity types in the same posting transaction (entry
of sender activities) and together with activity type categories
3 and 4.

How to fix this error?

Enter an activity type with a category valid for business transaction
&V2&.
<ZH>Note</>
If you have not yet carried out <ZH>any</> postings in actual or plan,
you can overwrite the activity type category defined in the activity
type master record <ZH>in planning</>.
This activity type category is then valid for the entire fiscal year in
both actual and plan. Making a change to master data at a later date
affects the <ZH>current</> fiscal year and therefore <ZH>not</> the
current posting.

Error message extract from SAP system. Copyright SAP SE.