The Pro Box remote is both bluetooth & IR. The way it works is the Box interrogates the TV over HDMI to identify what it is, then deploys the appropriate IR code to control it. Unfortunately if that fails, there's no manual pairing option.
This can be problematical with many TV brands now being manufactured by third parties. So for example the TV announces itself as a Toshiba but it's actually been made by Vestel, so Toshiba codes may not work. No idea what the recent history of Sharp is but I know that in the USA at least, they licenced the brand name to Hisense.
As far as I'm aware, there's no way to tell whether the Box has identified the TV & if so, as what. So you can't tell if the handshake between devices has failed or if it's just sending the wrong codes due to an ID mismatch. It might be worth trying a few more HDMI cables. Other than that, you may be able to use one of the older Humax remotes, as they also work with the Pro Box & can be manually paired using codes. No guarantee though.
