The Survivalist achievement works so long as you don’t die on your current level. If you died, none of the exp you earn for that level will be counted towards the achievement, and you wont be able to gain any progress on it unless you gain a new level and try again(pretty sure thats a bug but idk if its intended or not). You literally need to not die for an entire level in order for you to gain any progress.
Edit: Also, downed states dont count as dying