Messaging non I phone users

hi, I’ve always been able to message apple and non apple users from my iPad, but since Christmas messages to non I phones aren’t being sent and I’m not receiving them on my iPad. All messages used to come through on my I phone and iPad but now they don’t. I haven’t altered anything, and I’m missing messages now because I always use my iPad rather than the phone (numbers are too small to see on the phone, getting old!)

I would appreciate help from anyone.

Happy New Year to all.