No "poopy dance" or sniffing or circling or anything? My girls give off clear signals that they are about to do the poo. If you are watching him, you should have time to scoop him up and put him on the pad.
You may need to re-start training. Yorkies usually have regular times when they will poo, like right after eating, right after sleeping, or right after heavy exercise. Try confining him to the pad and giving him a vocal cue like "go potty" or whatever. When he does poo on the pad, give him major praise and maybe even a treat, but you don't have to treat. Loads of praise will usually be enough.
If you cannot watch him, then you need to confine him. You can do a search on crate training, and that may help. I will leash my Wosie to me if she hasn't pooped yet, and that way she can't wander off and leave me a "present" in another room. Then when I see the poopy dance, out she goes! And PRAISE PRAISE PRAISE for her! She's 10 months, and we are still in the process.
Think about how old HUMANS are before they finally get it! Patience is the key, my friend! Good luck!
