I've had the same problem for the last few times I've used my cooker. It seems that setting it up, trying and failing, followed by a long period of being unplugged 'fixes' the issue.
My experience yesterday: I use a small cooler as a cooking vessel. I clamp the unit inside, fill with water, and then plug in the Anova. I can connect the unit to my phone via Bluetooth and see the two temps. The current temp shows 32F and the Set temp shows 60F, same on the phone as on the unit. I can set the temp using the phone but the Start Cooking button is not active. I can push the manual start button on the unit and the circulator begins.The water gets warm over time but the current temp reading remains at 32.
I wanted to have pork chops ready to finish when I got home from church yesterday but was frustrated by the unit not working as described above. I unplugged it, disconnected my phone, and left it all set up on the counter. Later that afternoon, thinking I would try for dinner pork chops, I plugged the unit in and miraculously the current temp showed 92 degrees. I reconnected my phone, was able to set a target temp and time and started cooking. It worked.
I've had this unit a couple years (got it as a gift) and I'm not sure if it ever worked correctly right out of the box. I've always had to fiddle with it to either get it connected to my phone or get it to work at all. Allegedly you can set the temp and time manually on the unit using the thumb wheel but I've never gotten that to work either. Buggy and wonky but I haven't ruined any food yet, just been frustrated by the process.