I have the same issue. Mobile is not responsive. I contacted Phlox through their pretend chat function and received a response that Phlox is compatible with all versions of Elementor. However, it is clearly not working with Elementor 3.3.x. I did the same exercise as the person that opened this thread and can confirm, that for me rolling Elementor back to Version 2.9.x does in fact result in Phlox working again.
I also created 2 sample sites on Bluehost, one with the Phlox theme and one with the Twenty-Twenty-One theme with a simple 3 column section. The Phlox one is not responsive to mobile, the other is (I’ve also tried several other themes and all are responsive except Phlox).
I responded to their “chat” email with all of the above information and links to both of the sample sites… of course no response.
I think I will need to abandon Phlox and switch to Astra as Phlox for all of its features seems not reliable enough to commit to for the site we need to develop.