Everyone knows that the HTC one Max from Sprint is Sadly Well Sim Locked, and the Verizon HTC one max is Unlocked straight from the factory due to FCC regulations. On Sprint devives, even when you put in the SIM Card, it won't ask for the Unlock Code. It says Invalid SIM and wont let you use it at all. But I have found the way to Sim Unlock the HTC One Max for Sprint. It's really almost the same way as on the HTC One but with a few more steps.
Step one is that you have to be Rooted. Now, I am not sure if you have to be S-OFF or S-ON but I am S-OFF so you might have to be S-OFF as well, but you guys can confirm that for me.
Next is you need the Following apps: Root Explorer, Sprint HTCOne SIMUnlock Helper. You Must install them before continuing. You can get these Apps from the Play Store.
After that, you need to download the HTCOMADM_SPCS.apk File (I have attached the modded file in this Post). This file is the file that needs to be replaced from the one in your /system/app Directory. You need to Remove the HTCOMADM_SPCS.apk file first (Or Rename it) before you place the modded one in there. Once done, MAKE SURE that your permissions are set to rw-r-r and reboot. If you don't set the permissions right, it WILL not work.
After you replace the File, You are going to use the SIM Unlock Helper app next. After you select the app, it might say "Device Check Fail" in Big Red Letters. It might also say, "This Device is not a Sprint HTC One! Therefor, this Program will not run". This is ok. What you want to do is click the 3 Menu Dots on the Upper Right hand side and Select "Display SIM Unlock Log". It might ask you for Permissions. Make sure to Grant them. After that it will say "SIM Unlock Log". There shouldn't be anything there. Now hit the back button and now it should say Device Verified, Root Available etc. etc.
Next is you want to tap Start. If everything goes well, within seconds you should be in the OMADM Test Client. Scroll all the way down to the end and tap the selection SIMLOCK. The phone will freeze a couple of seconds and then return to normal. Once done tap the back button and the SIM Unlock Helper should show SIM Unlock Results. If it says Successful, reboot the phone (Although tapping Reboot might not work from the app itself)
Once Rebooted, Insert your SIM Card of your GSM Carrier and go to your Settings> Mobile Data> Network Mode. Once you tap that, Tap GSM/UTMS Only. If successful your phone will switch from Sprint to the GSM carrier. All there is next is to setup your APN settings to be able to receive the carriers data services.
PLEASE NOTE!!! That you won't receive HSPA+ (4G LTE) Data, but you will only receive the 14.4Mbps HSPA Speeds. Talk, Text, and Data should work with no issues.
Please Confirm that it works. I will be posting some pics up later of the process.
Credit also goes to chas123, he's the one who hacked HtcOMADM_SPCS (which is also used in Sprint HTC One SIM Unlock Helper) making it possible to unlock!
Also, for those who are having a vdm error. Replacing the original apk after unlocking fixes it. For those that flashed the ruu maybe replacing that apk will help also.