This helped me, I found it on another help page...
There's a very minor difference in the new link dialog which I think is causing this issue. On the old blip, when you clicked the link button, the box that came up was pre-populated with http:// -- but the text was highlighted (selected). So if you just used Ctrl-V to paste your link in, it overwrote the superfluous http://. In the new dialog, the http:// is there, but it's not selected, and the cursor is at the end of it. So if you do what you did before and just Ctrl-V without looking at the result, you'll end up with http://http:// and thus the link won't work.
Such a little detail, yet it causes so much hassle! Get into the habit of deleting the contents of the box before pasting your link, and you should be OK.
NB all this is based on using a computer, I don't have a tablet or smartphone so it could be different there.
Veronica 2