My bot is Dispenser 24, and it says it is warming up, then it tells me my security code that the bot should present me with. It won't come online, therefore I cannot trade with it.

Steam update causing bots not working again. We have corrected that.

Same here, with Dispenser 36. It's been offline for the past day apparently.

I noticed sometimes bots may failed to warm up. But most of the time it does for me. You need to wait like 10 seconds to get it warmed up. You might be trying when there was a tf2 update? It could be the reason. Anyway we will investigate the problem.