I managed to get it fixed on Monday. I had to re-download the initial software due to some other issue, but after that:
- I did a factory reset on the CP1604 (via TIA Portal).
- I loaded in pn2720.fwl from the J744 folder (located inside the Fanuc core software USB stick (shipped with the robot)).
- I made a GSDML file with cp1604_safe_fw2.7.2.zip (provided by Fanuc over email) in TIA Portal V15.1 (I figure this used the catalog CP1604 V2.7, but hey, it might be different).
- Downloaded the hardware configuration to the CP1604.
- Imported the GSDML file into my current project. Assigned matching Profisafe addresses and etc. (according to Fanuc's guide - R30iB Plus Profinet I-Device and Safety (CP1604) Configuration with
Firmware 2.7) - Downloaded the hardware configuration to my PLC.
And then it worked? I also disabled PROFIEnergy (whereas their guide says to enable it), but I doubt that was an issue.
I think the real issue was using Siemens' fw16xx-2.7.2.0.17.fwl instead of Fanuc's pn2720.fwl.