I pasted the url of the facebook post and when I selected the amount of ether then this message is shown.
2 Answers
I just had the same error using Facebook. I manually tested the URL in browser after logging off Facebook, the post link itself worked; but Rinkeby still didn't accept it. So looked like something wrong with Facebook parser.
I had to set up an account on Twitter. But even that I still got error at beginning. So I trimmed my tweet to fit into two lines. Bingo, it worked.
Try to use other faucets, like these:
m.
from the beginning of the URL host name.