Tub surround adhesive recommendation needed...green board?

[Cathy T.]

I will be replacing the elderly biscuit-colored tub surround in one of my units. When I bought the house, the tub surround had actually already popped off the wall, and was resting in the tub. I re-installed it three times within a week! I used Liquid Nails the first time, and Loctite Powergrab the second (both versions specifically had the words "tub surround" in the description). I used lots of tape to hold it up for longer than the time suggested on the adhesives. I removed the tape...and both times, within a few hours, it detached, and keeled over, and damaged things on the way down. The third time, I glued that sucker up and screwed the back wall to the studs! I found some small button-like covers to hide the screws, and it has stayed up for four years.

But it is time to remove it and do it right, in white...without screws and covers. I have been doing my reading, and watching YouTube videos in preparation...but nowhere am I finding recommendations for the right adhesive to use on the NON-drywall backing behind the surround. It's a green board of some sort, maybe a water resistant product? I suspect now that the adhesive (both types) was not the right stuff to use on this green board. (Also, I never saw any instructions back then to use a notched trowel, and it does not help that neither the wall nor the surround were perfectly flat.) But I think the wrong adhesive was the major culprit.

I will try to add pictures to this...

I think the pictures say it all. Can someone suggest a really good adhesive for this green board material?

Thank you!