after completing the biological assentation line I cant add Non-Hiveminded pops to the Hivemind. I don't know if I'm just being stupid or its actually not working can someone please help
I've done both of them and still nothing
You also need to finish the tech (genetic resequencing, I think?) which unlocks when you complete the biological ascension perk. The perk alone only gives you more trait points, the tech gives you advanced traits (including hive minded) and the ability to freely remove positive and add negative traits.
Also, there's a bug in 1.5 where pops still get eaten even when you're gene modding them. Try playing in 1.51 (the beta patch).