Cannot Reply to Private Messages. Why?

What's happened?

Some lovely posters have written to me recently and I have tried to reply. Yesterday I wrote a reply to one, but it wouldn't send.

I pressed SEND and got a drop-down message 'Gransnet says OK'

I pressed the OK box on that but nothing happened. It didn't send, no matter how many times I pressed OK. I have checked my settings and have no blocks on.

Anyone else experienced this? I could be missing a trick here, but I have never had problems replying to PMs before.

Can I just say now that I hope the lovely Grans who wrote to me don't think I am ignoring them. I really appreciate their writing to me.

Can anyone suggest what's happening please?