Ringtone Volume stuck on zero and greyed out. Please help

I have an unrooted 6P with android version 6.0.1
The ringtone volume is stuck on zero and greyed out.
How can I fix this?

Samsung S7 SM-G930K roaming greyed out

Hi all,

I am a newbie to this forum. I have got the SM-G930K from Hong Kong. It looks like the phone has the Korean Olleh Rom which I am expected. But I would like to have the Data Roaming turn on, however this option is greyed out and disabled. I would like to know if any of the expert has this issue? And how can I fix this? The reason I like this feature is because I am on Vodafone Australia they offer /per day roaming when I am overseas (in some countries).

Do I need to root my phone or is that something to do with the SIM card?

Thank you very much in advance!

Unable to change lock screen types, 'clear credentials'-option greyed out

Hi there,

I am using the simple swipe unlock method, but often that also unlocks your phone in your pocket. When it did unlock it did something and now I cannot change my screen lock type, when I open settings>lock screen>screenlock it asks for 'Confirm PIN', while I never set a PIN. I tried all the ones I would possibly have set somewhere, but it doesn't work. I read somewhere that there are other people unable to change their lock type, and the solution would be to clear credentials, however, that option is greyed out.

I deactivated and activated device administrators, I cannot encrypt and decrypt my phone, as some people suggest, because it then also asks for a PIN.

Does someone know how to tackle this problem without a factory reset?

I have a SM-G900F with android 6.0.1

Thanks!