I have just upgraded to v10 and find that I cannot login to MyPhone as any extension (I have tried five different). I have checked and the login details are correct, they work when used to connect a phone.
Wow, that's incredibly logical. And consistent with the 3CX assistant. NOT!! Since I don't have voicemail enabled on any extension, I have had to enable it, create a PIN, then disable it again.
you did notice it asked for a PIN and not authentication password? it has been this way since MyPhone was introduced to V10 at the start. There is nothing there to say otherwise.