The Dark Lord almost certainly did not know he was being lied to.
The Dark Lord, to the end, believed Snape was a very loyal servant of his. Even when he thought he’d need to kill him to master the Elder Wand, he actually regretted it, because he was killing someone he considered a valuable and faithful Death Eater. Though he felt no emotions over Snape, he thought him worthy enough of regret - if he thought Snape was disloyal, he surely wouldn’t regret killing him.
“Snape did not speak.
‘Perhaps you already know it? You are a clever man, after all, Severus. You have been a good and faithful servant, and I regret what must happen.’
‘My Lord –”
- Harry Potter and the Deathly Hallows, Chapter 32 (The Elder Wand)
When Harry tells him that Snape was actually loyal to Dumbledore instead, the Dark Lord is at first dismissive of the idea.
“Snape’s Patronus was a doe,’ said Harry, ‘the same as my mother’s, because he loved her for nearly all of his life, from the time when they were children. You should have realised,’ he said, as he saw Voldemort’s nostrils flare, ‘he asked you to spare her life, didn’t he?’
‘He desired her, that was all,’ sneered Voldemort, ‘but when she had gone, he agreed that there were other women, and of purer blood, worthier of him –”
- Harry Potter and the Deathly Hallows, Chapter 36 (The Flaw in the Plan)
If he knew when Snape was lying to him, the Dark Lord would have surely doubted his loyalty more, since his lies were told to hide his true loyalty. He may have known that Snape was using Occlumency to hide his thoughts, but he couldn’t have known for certain that Snape was lying and maintain such a high level of belief in his loyalty.
He probably didn’t know Snape was using Occlumency, either.
It’s never explicitly stated, but the Dark Lord probably didn’t even know Snape was using Occlumency on him. If he had known, it seems likely that he would, at least, trust Snape less than he did. It’s also possible that Snape gave him a plausible reason why he’d use Occlumency all the time and never be willing to “turn it off” momentarily for the Dark Lord to see his entire mind, but this too seems to be something that would make the Dark Lord less certain in his trust of Snape.