"For some reason, he cannot lose his virginity"
Because:
A: The author's an asshole and enjoys his readers in a perpetual state of blue-balled-ness.
B: MC keeps playing stupid fucking tentacle games.
C: MC wastes tons of opportunities.
D: MCs pretty dense. Not as dense as other isekai MCs, but dense.
E: All of the above.
It's
. Answered it for ya.