ZTE Zmax Pro Wifi Calling Issues, B04, B07, & B09 firmware


    I'm continuing to have Wifi calling problems with the ZTE Zmax Pro.  We've tried the B04, B07, and Jan 2017 B09  firmware updates.  We got a new phone under warranty and a new SIM card and still see the same problems.  I'm fairly certain it's an ongoing firmware bug.


    I used the Automate app to make a program to record when the wifi calling icon changes.  About 5-10 times a day, the calling icon either disappears, we get a REG99, a lot of ER081, or sometimes ER04 error (unable to connect).  Resetting the wireless settings and factory resets do not help.  After leaving and returning home, wifi calling almost never reconnects.  It usually gets REG99 then.  We have tried updating our E911 address, and it didn't help.  Putting in a SIM card from a different phone didn't stop the problem which stuck with the phone.  Rebooting instantly fixes the problem (wifi calling connects), although just for a few hours.


    We have the T-Mobile Wifi Cellspot router and have excellent coverage and Internet service.   I have a different brand T-Mobile phone that never drops wifi calling, and our previous phones had no problems.   I've seen the problems on wifi networks other than ours too.


    We have very spotty cell coverage in our house, so I don't know if that is a factor in confusing the Wifi calling software.


    I am waiting to hear from T-Mobile support engineers.  I hope this can be fixed in the next firmware update.  We like the phone, but we rely on wifi calling and are missing calls.


    MetroPCS users report similar problems on the ZTE forums... 

    MetroPCS B14 new update glitch | Z-Community


    Thanks in advance for any help!

      All replies

      • tmo_amanda

        Hey chopperc!


        Thanks for your thorough post of the issue along with the steps you have already taken to get your WiFi calling whipped back into shape. I'm in the same boat as you as far as relying on WiFi calling so I understand the level of importance that this issue holds.


        Do you have this issue while connected to other WiFi networks or is it primarily happening at home? Also, have you heard back from the Engineers yet? If you disconnect your WiFi Cellspot, does the issue persist?

          • chopperc

            Hi Amanda, the problem happens on any wifi network I try, not just our home network. The phone works fine for cell network calls.  When wifi calling is working, the audio is generally good. I wonder if the people who have bad wifi call quality are actually on a weak cell signal because the wifi calling has stopped.


            I no longer think our spotty cell coverage is related to wifi calling crashing.  The errors happen even if I set the phone to never use the cell network.


            I have not heard back from T-Mobile engineers in this. There has been no change in the problem.



          • I spent a lot of time in the ZTE Zmax Pro forum on zteusa com.  I thought I was literally the only T-Mobile Z981 user on there along with all the Metro people.  I had issues with everything from screen glitch to MMS on WiFi to wifi calling and hokey bluetooth and missing predictive text till the 09 update....for which the only issue fixed was the keyboard.  In the end, I gave up on that phone.

            • edwardp

              My apologies for reviving an old thread.


              I have two ZMax Pros with the latest update (B14). I have been getting ER081 errors for WiFi Calling with both phones, after the phone goes into sleep mode (screen turns off). As to how long this occurs after the phone screen turns off, I do not know. It will work, then after waiting a while, I will turn the screen back on, the WiFi Calling icon is red, with a notification of the error ER081.


              This occurs whether the phone is connected to my Comcast gateway (Arris), or the T-Mobile Personal CellSpot Router.