It seems Taonas' Ancient digsite is the only one that remains active. Both P3X-666 and P3X-439 are disabled :(

I'm also having trouble unlocking the Atlantis research, I got the ZPM from Taonos but no option for the research appears. I've done this recently in the base mod and I did the same steps there and it worked

EDIT ok the correct ZPM doesn't come from the digsite on Taonas, you have to get SG1 there and do a research for a few thousand credits, got it