@Viktor-Gal ELRS maintains compatibility between all versions with the same major version number, so a 3.x.x receiver is compatible with any 3.x.x transmitter; however, a 3.x.x receiver is not compatible with a 2.x transmitter. Because of this, you will need to update the transmitter in your handset. You can use the upstream ELRS firmware for this since we don't make any modifications to the firmware for the iFlight Commando, instructions are here. I suggest using the latest firmware version available, you can flash older firmware later if necessary. All customization and ModalAI provided models on the handset will persist through this process.

Hi @tkddnjs825,

In addition to Alex's question above, could you also please share which version of voxl-elrs is being used on each voxl2? The voxl-version command should list the versions of each installed package.

Can you also please confirm that in the voxl-px4 configuration file on the voxl2 that is not able to communicate with the ELRS receiver that the RC type is set to CRSF_RAW, like this: RC=CRSF_RAW.

Furthermore, if you could share the output of voxl-elrs --scan from the voxl which is unsuccessful that would be helpful.

Thanks,
Max