I do not know your phone, but as far as i know, there is no phone which supports ANT connections.
You also have to be aware, the number of simultaneously bluetooth connections is limited. How many depends on your device and version of bluetooth stack. So you should take care that no other bluetooth devices interfer your trainer. If you have turned on your trainer for quiet a while without to connect it to e.g. Zwift, it often turns on a kind of power saving mode and you not connect anymore. In that case just turn it off and on.
Just for reference: I have a simillar issue with my Wahoo Tickr, if it is connected via bluetooth with Zwift and I walk away so that it gets disconnected, it often happends that I cannot connect it again. In this case Zwift does not recognize the Wahoo Tickr signal at all, it does not show up in the list. Even if I take out the battery and do a hard reset, it will not connect with Zwift again. Maybe your problem is a simillar one.