I also have the same problem on m5stickC and m5stickC plus today. Everything was working fine two days ago when I last used it, and I did not change anything (same firmware 1.7.8, etc), but it just does not connect. I also tried changing the server between China and Singapore, but it did not make a difference. Any help would be greatly appreciated.
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RE: SOLVED: UIFlow cannot currently connect to any M5Stack devices