Please check the following:
1. Make sure that your audio interface is turned on. Whether your audio interface is running off of your iPad's power or from its own power source, check to make sure that all cables are securely connected.
2. Check your iOS privacy setting. iOS added the privacy setting for microphone access, it will ask your permission at the first time startup. On your iPad, go to Settings > Privacy > Microphone to enable it.
3. Try switching the input setting in BIAS FX. Go to Settings > Input Channel in BIAS FX and try switching to Stereo Input, Left Channel, Right Channel, Mix Left and Right. If your audio interface has its Instrument input on input 2, try setting the Input Channel to "Right Channel" and see if your guitar signal is detected by BIAS FX.