HI @Daniel_A1 welcome to Zwift forum.
Please start with the Android FAQ. There are two protocols you can use to pair to the Strydpod: ANT+ or Bluetooth. If you’re using ANT+, you may still need to install some ANT software on your device.
If you’re using Bluetooth: be sure that the Stryd is not already paired to either 1) the phone’s OS (like the way you’d pair earbuds or 2) Another app running on your phone. If the Bluetooth signal is already bonded to something else, then it’s not available to the Zwift app.
One other thing to check for: If you’ve installed Zwift on multiple devices, please makes sure you’ve logged off of all of them before using the one you want to actually use. Concurrent logins into the same account will also result in this sort of symptom.