You need to enter a space or more between your message and a hashtag in order to use it as a link.
There is a space between “Thank you” and “#”.
There is no space between “Thank you” and “#”.
How can I make sure that a hashtag is working as a link?
If you tap the “#” icon on the top left of the message screen, a space is automatically added. This way, you can make sure that your hashtag will function as a link.