My pop count seems to be stuck at 9,999. Despite buying new infra while at that number, it doesn't break the 10,000 mark.
The problem also seems to be cosmetic only, because despite saying 9,999 the game allowed me to build my 10th improvement today.
Thought I should bring this to your attention.
edit: Nevermind, the issue seems to have corrected itself, my pop jumped over 10,000 at update today.