If you take the DLPT, do you get the 25 points, even if you fail?

Failure is not an option. Plan to succeed.

Defense Language Proficiency Tests
If you are fluent in a language other than English, I highly suggest you take the proficiency test for that language. You must achieve a passing score of 1/1 in reading/speaking or listening to receive promotion points. You will receive 10 Army promotion points for each DLPT you successfully complete. These points are valid for 1 year from the month and year you earn them.

There's no failing, you're graded on a scale starting at 0/0. You have to score a 1/1 for points

AR 600-8-19
3 – 19. Civilian education
Maximum points: 135 for promotion to SGT and 160 for promotion to SSG.
f. Defense Language Proficiency Test. Twenty-five promotion points are granted to Soldiers who achieve a minimum limited working proficiency rating of 1/1 (listening, reading, or speaking) on the Defense Language Proficiency Test.
Promotion points remain valid provided the Defense Language Proficiency Test proficiency standards do not exceed 1 year (year/month) as of the point compilation month.

Cool youtube video, but when you start teaching promotion (or anything) to your Soldiers, they'll be better off just learning how to read the reg.