Hard to say what’s the problem from just this. Usually these kinds of errors happen when you have opened files in another program that UE wants to use, you don’t have access rights to the path (are you administrator?) or the directory is read-only. Often a restart of the computer also solves these kinds of errors. If that doesn’t help you could try to set the C:\Program Files\Epic Games\UE_4.26\Engine\Intermediate folder to not be read-only.