Have you tried doing a factory rest to make sure if that will fix the problem?. If so and u still have this issue, have u gone to A Rogers store or called Rogers so they can see maybe something on the account or area u live in may have a issue?
If u have tried all this, then ask them to send in the phone for repair. It could be the LTE chip causing the issue.
I did the full (hard) reset and now, I do see the LTE indicator for the first time since I got the phone. I must, however make the comment that a Rogers online tech was so adamant the the HTC ONE will never show LTE that 4G is the same, that he provided support number for HTC and I called them and they also indicated there would be no LTE icon.
Strange, though in the US the phones down there don't say LTE, but 4G or maybe 4G LTE instead. Different marketing spin here vs there, surprised the Rogers tech was spewing misinformation like that, as did the HTC rep apparently.