'never since then' is a correct phrase in written English
It can be used to express that something has not happened in the past or has not happened since a certain point in time. For example: "He has never had a break since then; he's been working non-stop for the past two months."
"I have never since then had to be concerned about how to occupy my time," she wrote in her memoir.
Never since then has he awakened with another person in his bed, and he is now in his 50s.
One, that night was falling; and I swear on this bottle that I have never since then (and many years have passed) seen darkness fall in the mountains without feeling an emptiness here in the pit of my stomach.
But I was unable to proceed because I declared that my house was flooded in 1979 – never since then – and cracks in the walls revealed subsidence in 1999, which was dealt with by my then and current insurer, Halifax.
Denise E., 8, who the suit says was placed in foster care after being removed at birth from her mother, was visited once by a case manager during her first week of life, but never since then, and has not received any services to monitor her care, needs or development.
Sarkozy's reputation as a friend of the rich who benefits from their largesse has never rescinded since then.
For instance, for The Wind-Up Bird Chronicle, the first thing I had was the call of the bird, because I heard a bird in my back yard (it was the first time I heard that kind of sound and I never have since then. I felt like it was predicting something. So I wanted to write about it).
I have never played chess since then.
She was my first girlfriend and I've never had one since then.
He stared at the Spinelli sign — "18K Gold From Italy" — and said, "We've never been hit since then".
The version that was in the room as the vote was taken has never been seen since then.
