Echo text using is_tag

That’s not what is_tag does:

Determines whether the query is for an existing tag archive page.

https://developer.wordpress.org/reference/functions/is_tag/

is_tag and other functions such as is_search etc don’t tell you anything about a post, they tell you if you’re on a search archive, or a tag archive, etc

So is_tag is true on example.com/tag/example but would be false on a post because that’s not a tag archive.

Instead what you want, is has_tag https://developer.wordpress.org/reference/functions/has_tag/

Some final notes though:

• Don’t hardcode term IDs! Use the slug/name if you really have to hardcode things. If you ever delete that tag by accident, or have to do a migration, your code would stop working.
• Indent your code, it’ll avoid entire types of bugs, and make it easier to read ( especially for people who might answer questions :p )
• If in doubt, check the official docs at https://developer.wordpress.org/