According to this; https://www.3cx.com/docs/supported-operating-systems/
They only support “x64”, by which I presume that they actually mean “x86_64” aka “AMD64”.
They also suggest that should-work, but not supported “Debian 8, kernel 3.16”, so I’m sure its not about the kernel version, but rather about having a cpu instruction set that differs from their proprietary precompiled blobs.
FURTHER, it looks like they “added” Linux support just from the previous-to-current version, which means that this really is windoze software.
I’d suggest that if you want to run a PBX on rockpi, you go with something more legit, like asterisk.