The ‘no space left on device’ issue is a problem with companion versions before 0.0.23, where mavlink logs build up and take up too much space to update. If you use the companion web terminal you can run
rm -r ~/telemetry to delete those logs, and should have enough space.
The ‘do you have an internet connection’ error message is a suggestion because the firmware failed to download, although in this case that’s more likely from the ‘no space left’ issue.
If you actually haven’t connected to wifi you can do that from the Network page). The upload and download tests from that page are between the companion computer and the top computer, and are unrelated to wifi.
You mentioned you followed the software setup instructions from scratch, so I’m confused as to how your companion computer is on version 0.0.22 (the latest is 0.0.26). Once you’ve connected to wifi could you try updating both companion and ArduSub from the System page?
Just for posterity, if there’s wifi near you but no options are appearing in the Wifi SSID dropdown then you’ll need to flash the latest companion software directly onto the Raspberry Pi’s SD card instead, after which you should be able to connect to wifi and update ArduSub. There are instructions for that here. The note at the top of that page which says “The latest version of Companion is v0.0.22” is out of date and can be ignored (we’re considering making the note auto-update but haven’t managed to yet) - the download link in the numbered steps is correct for the actual latest version (currently v0.0.26).
If we can’t help new users then our user-base won’t last. No need to apologise - you’re clearly trying to follow our steps correctly and something still hasn’t worked, which generally means we need to improve either our instructions/documentation or software. We’re working on both at the moment, but while there are issues they can be discussed on the forum - that’s part of what I’m here for, with help from the community members who’ve dealt with similar issues, and when need be the relevant software or design engineer(s)
That’s the hope. A community working together to build shared knowledge is much stronger than one with fragmented repetitions of the same questions and responses