Once I hit Continue, if I check it right away, it often doesn't seem to work.
I realized that I need to wait and check again a few hours later. If I do that, I find that the seat change is accepted.
And why is this a good use of your time as a traveller?
For the life of me, I don't know why some think that SHARES/.nuke/.pss is an improvement over .bomb. If I didn't care about which seat I sat in, I'd fly Southwest.
Since I do - and especially when I'm flying with my family - spending every other moment checking on seat assignments and flipping through several pages and links of crap to get to the seat pages that have my family's selected seats go awry anyway because of how poorly they cut over to SHARES - and no plane changes - just plain sucks.
David