Had this a few times now. Intermittently (and seemingly randomly) when a user joins a skype call their mute button is greyed out - so they are unable to toggle on/off.
Sometimes it works, sometimes it doesn't. All the required features on the phone are of course set to allow voice (as I said, sometimes it works with no issues). It's not a wifi/cellular issue - as this occurs on multiple networks and locations (i.e. home, office etc.)
Apps and IOS are all at the latest version
If the user logs off and rejoins 9/10 they are able to rejoin with no issues.
Has anyone else seen this or can offer any steps to resolution. I've done a general google search and others seem to have the same issue but i've yet to find a fix for it.
I have not seen this happen here. Although, I am not sure how many on our campus are using their phones to join conferences. I use my iPhone frequently to conduct meetings, but I have not seen this or had it reported to me at this point.
The current Skype for Business build on iOS updated about 3 or 4 (version 6.18.1) weeks ago does not seem very good to me. It constantly crashes on my iPhone 7. I have sent tweets to SkypeforBusiness and they said they would forward it on for me. I keep waiting for a new update to come out. Not sure if this is related, but thought I would mention it. I keep meaning to write up a post for discussion to see if others are seeing issues. Prior to the 6.18.1 update, it was a solid app on my iPhone... since that update, it is basically junk.
If I hear of anyone with the same issue you reported, I will follow up back up on this thread.