Ring doorbell 2 refusing to connect

Hi, my ring wireless battery doorbell 2 will not connect to Wi-Fi. Tried everything. Tried on different routers so no it isn’t that or internet. Password ok tried reset doorbell, everything up to date. Been working fine for months then suddenly stopped.. the chime is connecting all ok just the bell unit. Run out of things to try as tried everything oh support app. Any ideas or could it be unit is broken??? How long is warranty…had it 9 months now. Help before I go mad..thanks