Will this help about rfm7x-lib

[jnk0le]

If it is sending something, then it's a good sign.

In this case you are experiencing probably one of 2 issues:

1. Auto ACK, after booting, is set to be compatible with different chip than a second node uses (I guess that's a SI24R1 instead of whatever is printed on top of the chip)
2. Radio locks itself after 15 unsuccesfull retransmissions and clearing MAX_RT register is not followed by FLUSH_TX command. (only RF24::write() does it, and thus it works)

When using this library you need to take care of 2 options: RFM7x_MODULECHIP_USED and RFM7*_CONFIG_COMPATIBLE_MODE that need to be set to 0 to communicate with SI24R1.
I'm still not sure if it have to be set differently for normal and autoack payloads.

It should be also possible to use this library for pre initialization and then use regular arduino library, with taken care about FLUSH_TX command.

I'll try to finish arduino workaround port soon.