Contract has different purchasing organization &

What causes this issue?

The reference contract and the document you wish to process have
different <DS:GLOS.3526BFD3AFAB52B9E10000009B38F974>purchasing
organizations</>.
If the message you received was an error message, the purchasing
organization with which you wish to create the document may not access
contracts of the specified purchasing organization because the latter
has not been defined in Customizing as the reference purchasing
organization.

How to fix this error?

Depending on whether you received the message as an error message or a
warning, you can do the following:

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

If you received the message as an <ZH>error message</>, you can:
Assign the purchasing organization of the
<DS:GLOS.3526BFF6AFAB52B9E10000009B38F974>contract</> to the document.
To do so, enter the key of the purchasing organization that is assigned
to the contract.
Define the purchasing organization of the contract as the
<DS:GLOS.3526C03BAFAB52B9E10000009B38F974>reference purchasing
organization</> for the purchasing organization of your document. To do
so, contact your system administrator.
If you received the message as a <ZH>warning</>, you can nevertheless
post the document with the different purchasing organization.
In Customizing, you can activate or deactivate the message on a user-
specific basis.

Error message extract from SAP system. Copyright SAP SE.