I'm working on a challange entry and placed a spotlight with visible, volume enabled.  When I did a trial render with hdri lighting the volume light disappears.  What is happening?  Anyone?

Did you put  the light in the scene first and then add  enable the HDR function ?  If so, try reversing the process, enable the HDR first do a trial render pass, then add the spot. Although, HDR might just kill the visible volumetrics. I've never been crazy enough to do an HDR render with a visible volume light,.........I don't have 4 days to wait for the first render pass to finish !

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I've not had predictable behavior with volumetrics and HDRI yet. My HDRI version of "tsubo niwa" render in my gallery seems to work with volumetrics, but using volumetrics in another HDRI render didn't work. Maybe it's just one of those things.....

Maybe you could use a cone and give it a light-sensetive volume material rather then using a conventional volume spotlight?

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@ Rayraz, 

That might work as a cheat, but I don't think it would achieve the same look.  My past experiences with volume mats don't have the ability to maintain the shape of the primitive unless it is turned up full throttle and then it will have hard edges.   It just puzzles me that non-volume radials and such continue to work. 

It does the same for with regards to fog and haze, but once I click on it, the fog or haze setting, it come back!!!

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I tried to add volume spot after hdri enabled and still it is invisible no matter what intensity either is set to.   I'm thinking it may be an issue with the type probe used since Death-a-m says some worked for him and others didn't.

Are you applying any volume mats to that light?