May I know that are you using the latest version of Inkbird Pro? Could you please provide your phone model and system version?
Will the second ITC-306A be displayed if the homepage of the app is pulled down?
If not, please press and hold the up (wifi) button of ITC-306A until the PV displays APP and release it. The WIFI indicator on the upper left corner of ITC-306A will flash. Please switch it to slow blink mode.
Please refer to these steps: Q&A: Inkbird WIFI product connection troubleshooting
Can it work?