Hi good afternoon is not a bug the event knows as , Gene modification supply is an event just for some survivors and your question might be
" why just for some survivors?"
Potential enhancement is judged by system based on the current level and the current amount of serum when the player level is above level 45. If the level is lower than the server main level which shows next to your hp, activities will be enabled on player's interface.
In other words, this is a compensation to players who are weaker , i Hope you understand @karmic flame
Have a nice day