RTOS/CC3220SF-LAUNCHXL: SPI examples do not receive data correctly (data sent works properly)

Tool/software: TI-RTOS

I connected a CC3220SF-LAUNCHXL to a CC1312R1-LAUNCHXL. Running the spimaster and spislave examples on both, I don't see correct communication.

With CC3220 as slave and CC1312 as master, I see only:

Starting the SPI master example
This example requires external wires to be connected to the header pins. Please see the Board.html for details.

Master SPI initialized

Master received:

Which seems to hang forever.

With CC3220 as master and CC1312 as slave, I correctly see "Slave received: Hello from master, msg#: 0" on the slave, but on the CC3220 master I see:

Starting the SPI master example
This example requires external wires to be connected to the header pins. Please see the Board.html for details.

Master SPI initialized

Master received: 
Master received: 
Master received: 
Master received: 
Master received: 
Master received: 
Master received: 
Master received: 
Master received: 
Master received: 

Done

It appears that the MISO line isn't working, but I've triple-checked the wire and pin. (CC3220 P06 to CC1312 DIO8). Using the CC1312 with another SPI device seems to work properly, so I suspect it's something about the CC3220.