You have an 8 foot 1/4" line with 16 emitters and the last few aren't working? Sounds like there isn't enough pressure at the end of that line. I'd shorten the line length.

You can also try "backwashing" the emitters in case they might be clogged. Mommentarily hold your finger over them to stop the flow of water. This can allow the pressure to build.

Lastly, I personally don't care for the in-line emitters and 1/4" dripline. Seems I have better luck with the 1/2" line (with just a few, short 1/4" branches) and the normal emitters.

Do the math:

45 feet at 6" spacing is 90 drippers. If they are 2 gph that's 180 gph. At 50 psi 1/2" line is typically 300 gph
So at first approximation, you are running out of water.

Now, I've ignored pressure drop on the way to the garden. I've ignored the drop from joints. I've ignored that 25 psi regulators aren't always 25 psi.

Try this. Go half way down the mainline, and squish it with a C-clamp. If the emitters upstream from this work properly, then you are running out of water. Change the 25 psi regulator for a 35 or 40. Or replace your main line with 3/4"

Another possibility is that you got dirt in the line, and your emmitters are clogged.

As in the previous post, lack of water volume is the most likely problem. One thing to check is if the hose bib is on a 1/2" line which will restrict your volume. Try filling a five gallon bucket for one minute then multiply the amount by 60 to get your volume per hour.