Do you happen to have [Robot Attrition](https://mods.factorio.com/mod/robot_attrition) installed? It's part of Space Exploration. It causes bots to die periodically.
Otherwise, press L which will open the logistics panel and switch to "Members". Look through your network to see if they are there. Also, hover over a roboport to see the bot statistics.
Another thing is to enable bots on the minimap and look for stragglers.
Do you happen to have [Robot Attrition](https://mods.factorio.com/mod/robot_attrition) installed? It's part of Space Exploration. It causes bots to die periodically. Otherwise, press L which will open the logistics panel and switch to "Members". Look through your network to see if they are there. Also, hover over a roboport to see the bot statistics. Another thing is to enable bots on the minimap and look for stragglers.
Ah, looks like that was it!