It does sound like you just didn’t go hard enough. If you did the SS workout at the old ftp I would retest. Some days you eat the bear, and some days, the bear eats you. 
Can I ask…in your original post, you say you’ve been riding on an FTP of 149 for the past year. Is that right? You test once a year?
If that’s the case, I would say that’s something of an issue. It’s not necessary to test all the time, but to get the most out of training, it’s recommended you test every 4-6 weeks. As you get fitter, your body needs greater challenge (higher FTP) to continue to improve.