My iPhone 7 does not take landlines call forwarding. I have done this in the past many times before.
I can forward landline to daughter's iPhone 7 no problem.
Anyway, I star 72, wait and then dial my cell phone number- my cell will not ring for me to accept the forward- and yet my landline is forwarded to somewhere. I had my brother call me, the landline rang once, then nothing, but my cell did not ring.
I do not have airplane mode on etc.
Verizon help via Facebook had me unplug my home phone, do a network reset on iPhone, then plug home phone in. That did not help FYI.