for Moto X, the volume control for sound can not be increased. Media and alarm work fine and can be adjusted. No response anywhere near Ring Volume. Turned phone off/on several times. Is there another setting which could be preventing this? Or is this 3 year old phone just broken?
Make sure you have a ring tone selected.
I would put the phone in safe mode and test to see if you have an app conflict. If the phone works in safe mode, then starting hunting for the bad app. Republic Help
You can also try a few volume control apps on Google play to see if you can fix it.
Motorola also offers a troubleshooting section. Motorola Support - Find Answers | Motorola Mobility, Inc.
Last of all, you can try a factory reset before giving up. Factory Reset
You may want to consider this possibility before performing a factory reset: https://community.republicwireless.com/message/494873-re-moto-x-2nd-gen-ringer-volume-slider-in-settings-disabled?commen…
Problem solved, kind of…
I kept pushing volume control on phone up until “interruption icon” appears at top of display. It gives option of not interrupting for 15 minutes or never interrupting. It has gotten to "never, so I switched to 15 minutes and magically 15 minutes later the ability to ring returned. Strange that there is not an option to “always interrupt” which would avoid the 15 minute minimum reset. Anyway, I am happy with this.