After upgrading from CM 11 to CM 12 on my HTC One (m7spr) there was no data connectivity - at all. Fortunately, it is trivial to get working.
- Settings -> Mobile networks -> Access Point Names
If you do not see any APNs, you’ll need to toggle Airplane Mode on and off a few times, or set the “Preferred network type” to LTE in order to see them. Otherwise, proceed.
Scroll to the bottom and look for “Ting”. You should not be able to enable it.
Select “Ting” and edit it.
Change the APN type from “mms” to “default,mms,supl,hipri”. The “default” option allows you to enable it.
Save and enable “Ting” from the “Access Point Names” menu.
It can take a few minutes for it to connect but now 3G and 4G LTE should work.