Hi @danicas, welcome to the forum 
This is in fact a Companion Software issue (the latest stable version is 0.0.31, but it’s possible 0.0.17 might have had some issues with the standard updating process, or is just old enough that it ended up being broken by something outside our control). Note that our original Companion Software is no longer being developed - I’d recommend checking out BlueOS instead, which is a ground up rewrite.
For future reference, all our recommended software and firmware versions are collected together in our technical reference
If at some point you do in fact want or need to manually download a pre-built ArduSub firmware, you can do so from https://firmware.ardupilot.org/Sub/stable/ and selecting your flight controller board.