Never heard of it before but a quick search says it is another in the long list of Linux based "open source" handhelds, did not see what distro this one was based on though the chip at least (RK3326 https://rockchip.fr/RK3326%20datasheet%20V1.1.pdf
) is ARM based and reasonably potent so hopefully one of the better ones. Generally though these sorts of devices are not very special; send a few out to some shill reviewers, do a couple of updates and then take the money and run being how that usually goes for these sorts of things these days (older stuff like the old gamepark stuff got itself a bit of an open source following). On the other hand someone that follows all this more closely than I says it is one of the better efforts.
Generally speaking not all NES emulators are made equal. The NES is a very weak device when all is said and done and to help that the developers of games could and did use extra chips and things on the cartridge to expand its capabilities. On the NES these are known as mappers (technical discussion of some known ones if you are bored https://wiki.nesdev.com/w/index.php/List_of_mappers
) and there a loads of them, more being invented every so often or discovered (usually in odd homebrew and "Hong Kong pirate" games). Not every emulator will support every known mapper, and not every emulator will support every NES addon (the famicom disk system being the more notable in this). The various portable devices then being notorious for not supporting all the mappers vs PC where most things tend to be supported.
This is usually what the problem is, and if you are asking this on a ROM hacking site then I presume you also tried a hacked ROM that might be causing the trouble. Hacked ROMs can change mapper (some mappers add more than others, and as devs had to pay more for fancier mappers where today it is all software then hackers are free to change things). Sometimes hackers also make ROMs that only work on certain emulators but fail on more accurate emulators or original hardware, though this is usually more of a problem for the SNES.
So yeah check your ROM on a PC to see if it works there, if it works on PC try updates for the device you have (official or unofficial) or give up on that particular version and play something else.