If your phone accepted the code received from us but you experience No Service issues (you do not have any signal with the new SIM):

1. Put the battery cover on. For the most of the HTC models the antenna is in the cover.
2. Double-check that the SIM is activated and properly working.
3. Sometimes misconfigured network settings can be the cause for this problem. Consult your phone manual and check these settings; usually a Factory Reset can do the job.