Which one? https://downforeveryoneorjustme.com/transfer.sh says it's up and fine for me.
If you're curling don't include the last character that the URL has in response. That's effectively a carriage return/end of data
This is what my dig shows
`transfer.sh. 2 IN A 0.0.0.0`
Probably your DNS blocking it then
Seems like my Pi-hole blocked it.
It’s back! I thought it stopped nov 30, 2018? +1
Indeed, they had a bit of a hiatus but the service was brought back.