Hi Hive account@grimmlocke !
I had troubles with dtube at first and I found what worked for me (on a windows laptop) was using google chrome in private (incognito) mode, and making sure I signed into dtube using the 'sign in with steemconnect' option.
I made a post about it here..
https://steemit.com/dtube/@nicolcron/m2ueso7j
...but I pretty much just told you what you need to know already! :)
Worked for me, I hope it helps
Good luck!
(p.s. if you watch the video I mention about leaving the window open all night to seed the video, you DO NOT need to do this anymore, there has been updates since then.
p.p.s. I did have it fail one day and eventually found that deleting the cookies from google chrome got it all up and running again!)