Causes of stuck fermentation can be dead, unhealthy, or too little yeast pitched.
According to their yeast calculator, you under-pitched.https://www.lallemandbrewing.com/en/canada/brewers-corner/brewing-tools/pitching-rate-calculator/
That may or may not be the cause in your situation. The packet states to store @ or below 4c (39.2).
I just received packets of W-34/70 in the mail. I brought the packets inside and used a lazer infrared temperature scanner.
The packets were 95f degrees (35c). How long were they at that temperature ? were they higher at one point ?
How much did they cool down before checking temperature ?
My point isn't to debate about proper amount of healthy yeast to pitch.
A brewer could be possibly pitching at a much lower rate than thought, due to dead/unhealthy yeast damaged from heat.
Some yeast packets are already pushing the limits with good dates, and stored at or below 4c.