I have the same issue along with a few others I’ve spoken to. I was lucky enough to talk to the owner of Syzygy and he knows about the issue and is working on a fix... I own the 870 and love it as well!
I received an email from Syzygy with instructions on the firmware update for the sub as well as the new version of the app. The instructions are pretty straight forward. Make sure you have a USB jump drive to copy the file onto. You'll then plug the jump drive into the port on the bottom of your sub. The update happens automatically. Everything is working fine again. However, I have noticed when the sub turns on, there can be a loud thump. Overall, Kevin at Syzygy was very helpful through this. I LOVE the sub by the way.