So I did some research, and I think basically the culprit here is ad blockers not playing nicely with vimeo's privacy settings. Ultimately, if it's a persistent problem, this is an issue for vimeo support. Here are two links and a few forum comments from Vimeo's site:https://vimeo.com/forums/help/topic:121217Some of the forum comments: - If you are having this issue you should check if you are blocking tracking cookies in any way. In my case it was the Firefox add-on "Privacy Badger" that was blocking the Vimeotracking cookie.- Using "Privacy Badger" and telling it to allow vimeo's cookies will solve the problem.And: https://vimeo.com/forums/help/topic:281401 — two apple iOS issues that are now resolved. Hope this helps!