I need an advice for my current training plan. I’ve been through base and build and have a team-time-trial in 2,5 weeks. The last block of my build phase were amazing and it was the first time I had the feeling of a “spot on ftp”. After the rest week (between build and specialty) I felt good and recovered. So I tried my first threshold workout but I couldn’t hit my intervals. I managed to get through them slightly below ftp. The workouts after it (2xthreshold and 1 SS) felt amazing and I thought I bounced back to my old fitness. But this week the same thing happend. I had to train indoors I had to quit after the second interval. I finished the workout with riding the threshold intervals at ss after I caught my breath. I haven’t been able to fall a sleep for two days. So what should I do? Im currently at mid vol 
Maybe you 're tired!
And you’re expectations are too high, considering you are starting a new phase.
There’s zero benefit in pushing yourself to try for the desired Watts if you can’t maintain it for the interval duration.
Lower the intensity so it is hard, but achieveable and allow your body to get used to the higher intensity that Threshold is.
As for not sleeping, that’s a sure sign of overtraining /stress /anxiety.
Try not to worry about it, and make sure you get some rest and recovery before your TTT.
Good luck! 
It sounds like your first workout where you struggled may have just been an “off” day for you – it can be tough to get back into higher intensities after a recovery week.
When you were riding indoors, did you have proper cooling? Training in a cold room with a powerful fan that can move a lot of air is key to nailing those trainer sessions. Some athletes even prefer having multiple fans pointed on them – it makes a huge difference!
Make sure everything off the bike is dialed in too – nutrition, rest, recovery. Lack of sleep sounds like there might be some stress in your life, so if you need to take a full day off from training to recover 100%, I’d say go for it – especially this close to your A race!
You won’t gain much fitness in these last couple of weeks, so really focus on recovering as well as you possibly can so you feel fresh for your TTT. 
Thank you for your suggestions! @ZackeryWeimer my indoor fan setup is definitely not optimal and it felt like overheating. My wahoo said something around 23 degrees celicus as an average temperatur. Eating and rest can further get improve but is something which I’m generally trying paying most of my attention to. What worked for me was to talk to a psychotherapist because the workout felt (retrospectively) like a threat to me and the bad sleep/dreams were an indicator for an anxiety/panic attack (ty for the hint @Lydiagould ). Currently I’m feeling way better and I had two test races which went really great. Its still an up and down and fighting the urge to overinterpret hr and my health but its getting better 
Gotcha, 23C isn’t bad on its own, but it can sure feel hot without excellent cooling! Industrial or high-velocity fans are definitely worth looking into if you do a lot of your training indoors.