No availability check can be carried out for material &

What causes this issue?

The material &V1& (plant &v2&) in item &V3& which you entered for
processing &V1& (Werk &V2&) is blocked for another transaction.

System Response

The system is therefore unable to carry out either the availability
check or the transfer of requirements.

How to fix this error?

After you have determined that the block on the material has been
removed, you must start the availability check manuallly inorder to
complete^ the processing of the transaction. This can be done from the
schedule line overview.

Error message extract from SAP system. Copyright SAP SE.