Fermentation riddle

[Tippy-chea]

Brewed up 30litre all grain stout done many in the past put 15litre in one closed fermentor and 15litre in another, aerated etc applied yeast white labs Irish ale in one and mangrove jack's lager (dry packet) in another, so dry yeast fermented fine the white labs no movement after 24 hour.
Spoke to a friend who works at whitelabs he said leave another 24 hour and re pitch of no movement so re pitched with California ale white labs all I had left another 48 hour no fermentation so repitched with mangroves dry and still not fermented so my last hurrah has been using the spent yeast from the other batch.
So to summarize why would one ferment and not the other all come from same kettle at same time. Only variable is the one that hasn't fermented was the first out the kettle other than that been identical
It's left me scratching my head and £20 in yeast down it's been a week of no movement and no moulding either

 

[Tippy-chea]

Also the whitelabs been kept on heat pad at correct tempt etc like I've done many time before

 

[ncbrewer]

Maybe your White Labs yeast is too old or got warm for too long. You could try some of the dry yeast.

 

[Saunassa]

@Tippy-chea so what was the outcome? That is a lot of yeast in 15 liters. Did you check the gravity and see if it was done faster then you thought? Plus how sure were you about the seal on the fermenter?