I received a Here2 in the mail recently. My Cube is an older version (but has the most recent firmware) so I plan on using the CAN2 port.
My new Here2 was already switched to CAN and the 4-pin cable was already on it.
I was able to load the Here2 in the SLCAN interface and run the bootloader process. Solid green LED’s after a couple of minutes. I waited another minute to confirm, no changes. Rebooted AP and reconnected.
Then, I pulled up the Here2 in the SLCAN interface again to begin the hex update. The progress bar began moving across the progress window for several minutes. The window went away after a while. I waited a few more minutes…rebooted the AP,
Now, I have a white LED and green LED on the Here2 and am not able to pull it up in the SLCAN interface, nor do I have GPS connectivity. P1 driver set to “1” and GPS set to “9” (CAN).
Keep trying to connect it, what version of Ardu are you using ?
I have seen some really odd things with some of the later builds and SLCAN. Try installing an older daily build of Ardu from June 2019 or so and see if it lets you connect.
Make sure your are also updating to the latest beta version of Mission Planner there are fixes that are done that aren’t loaded unless you get the latest beta or there is major release that MP tells you to update. As @MadRC said there are some funny things with can but I have noticed major imporvements in the past few beta releases of MP you can also try the UAVCAN GUI tool I have had luck on there.