Try the restart by holding the left and bottom right buttons until the Fitbit logo appears. If nothing appears then do it a couple more times. If still nothing -> consider trying a full reset to new by holding all 3 buttons then releasing the bottom right button when the Fitbit logo disappears. Wait until the watch vibrates then release the other buttons. The reset to new is normally a last resort option. Be aware that your issue with a black screen is quite severe and your Ionic is in a pretty bad state. Only proceed if you are ok with taking these risks to make it better. Sometimes you can make your situation worse.
Calling Tech Support at the number below might be a better option as they can take you thru different troubleshooting steps and record everything. Sometimes that is better but sometimes it is a waste of time. Tech Support has helped me about 30% of the time. The rest I solved myself or was left unsolved in the hands of programmers to change code or do nothing. Check out this thread for more info about resetting etc,
https://community.fitbit.com/t5/Ionic/Resetting-Your-Ionic/td-p/2232205
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Really there is no need to suffer in Frustration - simply call Tech Support at 877-623-4997 and get your Ionic replaced right now while you can
Many have followed this straightforward advice and now have a replacement Ionic - we all should have “zero tolerance” for any defective Ionic
