How to allow phone to send sms to short code again

[Trosgol]

I have a Sony Xperia Z1 Compact and am unable to send 5-digit short code SMS texts. I just keep getting a message "could not send". Up until April, it used to work.

I have tried my sim in my wife's phone and it works fine. So now I know the problem is with my phone's settings but can't find what to change. All normal SMS messages incoming and outgoing work fine. My phone is with Virgin Mobile (piggy-backed on EE). I have Android v5.1.1. Latest version of Sony software.

I've seen your solution: You should try clearing the app to default.  Menu > Settings > Apps > All > Messaging > Clear Defaults

However, when I press Settings>Apps, it lists all the Apps and there is no 'All' option.

[Uliwooly]

@Trosgol

I think I've seen that before with another user and virgin mobile, if I recall it was on the network side, you can use the search bar to find the post. 

[Trosgol]

I found the post you mentioned and it was a slightly different problem. It was SMS in general and I mentioned in my earlier post that the solution for that post I is not possible for me.

[Uliwooly]

@Trosgol

could you test your phone in >>> safe mode

[Trosgol]

Thanks, I've followed your suggestion but it doesn't solve the problem. The one thing I don't want to do if I can avoid it is a factory reset. I think I'll just live with it if nobody comes up with another suggestion to solve it.