Can yeast die if too long in primary?

[Beerbuck]

It is possible if I let my yeast too long in secondary, when its time to bottle the beer it dosent carbonate after couple of week? This new to me and sometimes a beer get carbonated and one is not on the same batch? Or it could be my capper?

 

[NiteOwlBrewing]

Are you making sure the priming sugar/DME is mixed well after cooled?

 

[Beerbuck]

Im stiring it for like 1 min before bottling and stir a couple of time while fulling the bottle, is this enough? For sure sometimes im not stirring so much cauz im a little drunk haha