One person can't text me
OK - long story
I'm texting my friend's mum to organise a baby shower. The mum can get my texts, but when she tries to reply it comes up something like "message sending failed" or "message not sent".
I think the mum just has a plain feature phone but not sure what kind. I have an iPhone btw.
But why would she not be able to text me? I haven't blocked her, and she's trying to reply directly to my message? Any ideas at all ????