VG is very viscous - thick and gloopy. To make it work better in a PV it is thinned with distilled water, alcohol, or flavorings that are themselves very thin. It needs about 10% added to make it easy to use, and some add 20% water etc. Anything added will thin it out, so maybe the flavorings by themselves will fix it.
Because of this, you never order VG base at the actual strength you want it, because some comes ready-thinned, some comes gloopy, and you won't know which it is unless you have previously ordered it. Order 1 strength above what you need. If you are one of those who uses a lot of flavorings (like 20% or 25%, as some do), then order it two strengths up, as the final mix will be well-diluted. Maybe just play safe and get 100mg, then you are covered. Be careful when using 100mg base unless you know you have a high personal tolerance for nicotine.
If we are talking about premix flavor liquid here, then maybe it's best to ask the vendor if it's thick and gloopy, or thinned out. Thick VG may not work in some carto tanks unless you Dremel a couple of slots in the cartos. Also drip some thinned-out liquid into the top of a fresh new carto even when it's going in a tank - thick VG can take some time to wet out the filler.