HTC sensation 4g is unable to get the mobile network

I have a HTC sensation 4g which I bought 2 months ago. It has a great accessing speed. Recently I updated my phone to android version 2.3.4 (gingerbread), after updating it reset everything. But now I cannot connect it to my mobile network.
After updating completely doesn’t know why the whole network is lost, I can’t see any 4g kind of thing on the screen. It says that it won’t connect to the mobile network as, initially before updating everything was working fine. I think there is something wrong I have done, can anyone let me know what could be the mistake.

Yes there may be some kind of mistake or small things you need to correct after updating your phone. In your phone there must be a notification bar, pull down the notification bar and make sure that you have checked the network box. If checked then switch off you phone and then again switch it on, and leave the phone for a while with doing anything. It’s because the phone takes some time to get resync so have some patience. I am sure you will soon automatically get to see your network. If this doesn’t work then you will have to look out for some other solution.

Sometimes it happens; disappearing of mobile network is one of the most common problems. In fact you must not take it as a problem. It happened with me many time due to network traffic or when my mobile gets hanged. During that moment I never get panic instead I just switch off my phone pull out the battery then again insert it and switch it on and wait for the phone to sync, what else, my network comes back as it was.
Even if this doesn’t work then why don’t you contact a customer care online and get in live chat with them. This will definitely help you to sort out your problem and also clear all your doubts by having face to face encounter with them.

Similar problem with me too. But it happens most of the time especially whenever I travel from one place to another. But I sorts out the problem easily. I always try out the Network search option; here you just have to allow your phone to search for the required network automatically if you can’t find the concerned network in the network list manually. It’s very much simple to do so, just go to wireless and networks option and in this option you will get certain options, Wi-Fi, mobile network, Bluetooth etc. select the mobile network option and then search for the lost network.

I am not getting how people can say that they sorted the problem in their phone while facing the same problem which I am going through. I have tried all the possible option including the solutions mentioned over here above. But noting worked, not I am scared whether my phone is facing some serious issue other than what I mentioned above. Thinking to perform a factory reset, because that the only option going into my mind. Is there anyone who agrees with me, should I do a factory reset in my phone?

Yes definitely, if you have tried almost all the possible option then you should undoubtedly try out the factory reset. Maybe after factory reset, along with all the default setting in your phone your network will also resume. if this doesn't work then contact the care center instead of trying out some other alternative option. By the way may I know which ROM is installed in your phone.

I will suggest you with a solution. Try it anyhow, hope so it would work:

Go to settings
Wireless and networks
Mobile networks
Access point names

after coming into this option make sure that "tmobile data disable" is not mentioned anywhere and also the setting under it doesn’t mention “disable”, if you see any such things then click and change it vice versa. After changing the option reboot it however. If this isn’t the problem then make sure that your mobile network is checked off.