Hi there. We had the same problem. Searching through this thread and so many people had the same problem and we are also connected via ethernet although that shouldn't be an issue.
We sorted the problem with a hard reset via the on/off button on the back of the tivo box. We switched off and to give it time I ran a speed test on my smartphone to check the speeds. The speeds was good around the 150 megabit mark.
I then powered back on and the reboot is quite lengthy but it worked. Also youtube was quite long rebooting but the buffering circle only appeared momentarily.
Maybe this will be a temporary fix due to a larger glitch but it fixed the rotating circle problem.
I actually called VM Support and they eventually managed to fix whatever the issue was and I haven't experienced it since (it was a long time ago). It's still a tempermental service though as I routinely get dumped from Youtube sometimes after a very short space of time like 10 minutes but more normally 50 minutes / hour but I'm living with this.