I would guess it's the glazing putty solvents pushing up through the primer, keeping it tacky.

What was the thickness/depth of the glazing putty? Dap-33 can take from 4 to 6 weeks to skin over enough for paint.

Did you remove the contents (the putty) and stir it well before application? Was the tacky window your last one? If so, most of the solvents that settled on the bottom of the can is keeping it tacky.

I abandoned the oil based putty many years ago and switched to Aqua Glaze.

Here is a link that might be useful: Aqua Glaze

If the oil is still drying in the putty, the primer can't dry. But if the non-drying isn't just at the puttied area, then some other factor is in play. If you used any kind of stripper and failed to completely remove or neutralize it, that will cause the paint to not harden or fail prematurely.
And, of course, externals also play a part in getting primer to harden. If all of the primer wasn't drying right, I'd suspect the paint itself. When you get primer tinted, especially with black colorant, it's a very good idea to thin the paint and add japan drier to encourage it to harden. This is for oil primer only.
Casey

I finished a tub of DAP 33 during the process, possibly on this sash, I don't remember.

Reading between the lines of both responses, it looks like I need to remove the painted-over glazing and redo this sash.

Ouch, Aqua Glaze is $25 quart delivered; $112 for 6 quarts. And not sold locally.

Sigh.