I have used this line of code before release of iOS 10.3 ,and worked fine.
NSMutableAttributedString *attributeString = [[NSMutableAttributedString alloc] in
it is the bug in iOS 10.3 , NSStrikethroughStyleAttributeName (any NSUnderlineStyle cases) is not working any more on iOS SDK 10.3.
if anyone found the updated answer related to this , please inform here, I will update my answer.
Product Version: 10.3
Created: 14-Mar-2017
Originated: 14-Mar-2017
Open Radar Link: http://www.openradar.appspot.com/31034683
Radar status is Currently Open state
you can see the alternate sample also here may be it useful.