I’ve read about this issue a few times now. So I’ve rebooted. Checked cable connections. Changed remote batteries. But it’s still an issue.
It can sometimes take 1-2 mins for the remote to start working.
Sometimes it starts on a TV program, other times it’s a blank screen. Very frustrating. It’s clearly a known issue as so many people have reported it.
The only time I've found it took a long time for my TV Box to boot (and consequently get its remote to work) was after a very recent box software/firmware update. In the settings for my TV Box Pro there's an option to manually check for updates, both for the box and for the apps - I suggest you try running both of these. If an update isn't available or any update doesn't fix the problems you're experiencing, my TV Box also has a field all about the Bluetooth Remote under settings (accessible through the gear shaped icon on the top right of the box home screen). It'll depend what model of TV Box you have - this info should be in your TV Box settings but it may not be in plain English eg my TV Box Pro is described there as a Sagemcom RTIW387. What does your TV Box Device info screen say you have and what does the Bluetooth Remote page say?