this morning I wanted to see a video on my imo from my friend and I could hear his voic in the video but no picture but after that any bottom on my phon don`t work .I even can not shut my phone down.
I don't use IMO messenger, but I see in the forums it may have some issues on Windows Phone.
Try a Soft Reset. Hold the Volume Down + Power buttons until the phone vibrates and reboots (about 10 seconds). Soft Reset is a great go-to to solve many types of glitch. You do not lose user data.
If Soft Reset is not possible, pull the battery if your phone has a removable battery.
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