After upgrading my ASUS Zenfone 5 to Android Lollipop, I am unable to access HSPA/3G data. In Brazil we have to manually input APN settings, and when I try to do so, I receive the following message (in Portuguese, here tentatively translated into English):
Access point Name settings are not available for this user.
As my phone is rooted, I have tried solutions proposed by this topic and also by this. None gave me results, even provided that I followed every step without any errors or warnings (chmods and chowns were all effective and edits to content://telephony/carriers were persistant). I also tried to re-generate telephony.db file by deleting it (thus forcing Android to populate it again). A factory reset (as suggested here) had no effect as well.
So far I have nothing to celebrate. My only access to internet is Wifi at home and at work. No mobile data access, and I know it is available (this week I had a try with CM12.1 and data connection worked perfectly. Unfortunately had to revert to stock ROM because CM12.1 is still too buggy). No better suggestions came from googling around other sites and forums.
I hope someone can give me some light over this issue, as I should rely on my mobile internet access to perform various things when commuting or away from wifi.
Heads up: the bounty was automatically awarded by this site yet the problem was not solved. Still awaiting a valid response.
Final update: please refer to my answer a the bottom of this page. The problem is (finally!) solved by the latest (v. 188.8.131.52) released by ASUS.