I'd like to thank those who offered suggestions here. I too was unable to "confirm" the slotting of the warrior trait although I had enough marks etc. A few days ago I opened an in-game ticket which was responded to and promptly closed, but the instructions didn't help, so I opened another ticket, referencing the other ticket # and asking for more help, and there has been no response.

After checking this forum I just completed Defence of the Prancing Pony on one of my characters. I had tried on a total of 4 so far and only 1 had completed it, and now that I understand what's going on I realize that character is a new toon for whom I haven't yet built a trait tree. All the others were higher level older toons (I just started playing again after a several year hiatus) who already had trait trees assigned. Those trait trees are clearly the culprit for this bug in confirming the warrior trait purchase.

So I went into my trait tree and selected tree #2 which was blank. At that point I was finally able to hit "confirm" after slotting the warrior trait whereas previously the "confirm" button had been greyed out. Then I continued with the skirmish only to realize that many of my spells/skills were no longer in my toolbars since they weren't equipped due to the trait tree change. The skirmish is easy enough to get through without those skills so I finished.

I had planned to set Skirmishing aside since the problem was aggravating (and sadly Turbine wasn't much help) but decided to reacquaint myself with my level 60 Lore-Master. She had left off from the epic quest series at Vol. II Book 5, Drums in the Deep, so I went on my merry way to Moria to do this and guess what? It's a skirmish and you can't do it unless you've completed the skirmish training!

I am now about to attempt to continue with that quest line using my #1 trait tree with all its spells/skills and am seriously hoping it works. If it does not I will update this post to share more info.

Once again, thank you for your help in sorting this bug out since Turbine clearly is in no hurry to fix it.