Warning! You have not done the checkout with the current model

What causes this issue?

The model that you are currently working on is not the same as the
model that you checked out.

System Response

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

How to fix this error?

You can cause this problem to be ignored if you set the "Forced Mode"
when you copy the model back.

Error message extract from SAP system. Copyright SAP SE.