I like the nice blue color on your coil.
Sorry if I wasn't clear on the sigelei and it happens with Pico if even at same wattage.So it could be 15 watts just isn't enough power.
The vapor production is thick and cloudy but tempatures are too cool.
Mine does same thing and anything below 1.3 ohms shuts it down.
Im using 27 gauge now,1.30hms,I'll try 29 gauge and see what happens.
I have a nautilus clone but it vapes poorly and needs drilling.
Think any dual-coil arrangement is going to put you below 1.3Ω wtih 29 or thicker. I've run Immo's on Sig's and Vamo 15's with single-coil. Sorry perhaps I should have been clearer. On your Pico I'd go for the sweet spot (see Mod range | Steam Engine | free vaping calculators) for the res target. Prolly between .7-1.2Ω. Not sure which eleaf spec best conforms to yours. Hold off on the 29 till you find the power range center. A 27x1 10/9 2.4mmØ = 1.409Ω will let you try a single in the 454 with the Sig.
Good luck and nudge us if need be.
p.s. That blue color is where you want to be covering as much of the coil as poss except end turns. Just fire it up at low voltage and it'll happen. Whistle on it if need be.