iPhone 6 will not ring on incoming phone call

Sorry, I forgot to mention, volume is at max. There is a setting amiss.

Whatever the volume settings are, the physical switch on the side turns ringing off.  Did you check this?

on the left side of the iPhone 6 I have up and down volume buttons. When I turn it down to zero, it reads "Mute." Right now, I have it at max volume, yet it's set (somewhere) to vibrate.

I'm stuck and need an iPhone expert.

I have the Up Down Volume buttons on my phone. That controls volume as you say.

Above these two buttons is a silver slide switch. If it is showing orange, then ringing is muted. Try it and see.

https://www.dummies.com/consumer-electronics/smartphones/iphone/the-controls-on-the-sides-and-front-of-your-iphone/

that's an older iPhone, it seems. I am iPhone6

I have an iPhone 6s.  No such slide switch for you?  Strange because that is how we all turn off a ringing phone.

I suggest you visit the Apple Store and ask them.

i do have a toggle, sorry. I thought it was a port that I never used.

It's working now!

Thanks :)

Thanks.  I am glad you found it :)