May I know are you using the Inkbird pro app?
Have you changed your router settings/phone settings/ location of the IBBQ-4T?
Please note that the IBBQ-4T is required to remain connected to the 2.4GHz wifi router after a successful connection. The router is able to access the internet successfully.
If you delete the offline IBBQ-4T in the app and re-pair it via AP mode (slow flash mode), will it work?