Wifi - Mobile data issue

[AC Question]

Hello, so i have bought an htc one m8 mobile recently but i got surprised to see that it had supersu installed in it , anyways i used it as normal to find out that when i connec to a wifi some apps like tv remote for example can't connect to the server , whatsapp can't download photos but can download videos , when i check for an update while connected to a wifi it says up to date but when i turn off wifi and use mobile data it finds a new update.
the stranger thing is that if i create a hotspot from my other phone and connect this one to it , it works fine although it is connected to the hotspot through wifi.
so i removed the root using universal-root remover (from google play) but still same problem , (android 5.0.2) i tried updating but it says that the software version is modifed , but when i go to the boot loader it says software status official , boot loader locked , cid 11111111 , m8_ul pvt ship s-off , i tried flashing the stock ruu from the official htc website( i used the t-mobile version cause when i searched the mid it looks like t-mobile but the device is unlocked) but it gave me unregistered error.
hope you can help thanks you in advance.

 

[Rukbat]

Regardless of whether it's locked or not, is it branded? (A TMobile brand makes it a TMobile phone, locked or unlocked.) The RUU must be for the particular phone you're flashing it to - a TMobile RUU won't work on an unlocked AT&T phone.

(That's all secondary - if you bought it as a new phone, it's a used phone - Android phones don't come from the factory with SuperSU installed - and SuperSU doesn't make the phone rooted, it's just an app. The file su, in the bin or xbin folder, is what makes it rooted.)