Board Game Arena

I've only played a couple of games and thought I would try the solo mode on BGA. I'm in the last round and wanted to upgrade my house from clay to stone. When I started the round, this space showed as available, but after I used a family member to gather stone it showed as greyed out. I'm just trying to figure out why...I've made several mistakes in this playthrough, which I expected as a newbie, but this one baffles me.

I don't know if the URL is the correct way to link to the game, but just in case, it's here: https://boardgamearena.com/tableview?table=904550223

This game has been around long enough that I suspect it's some rule I don't know, but I'd like to find out what it is so I can account for it next time! Thanks for any insight you might have.

Edit: This issue happened on turn 175. I gave up trying to figure it out & just finished the game another way, but I'm still curious.

You can only rennovate from Wood-->Clay and then Clay-->Stone (there are of course some special cards that can break this rules, once you play with hand cards as the game is intended, i.e. not Beginner Mode).

If you had 4 clay 1 reed you would have been able to renovate.

Interesting. For some reason I thought I had already upgraded to clay. Even now I distinctly remember deciding to do so, but I must have imagined it, or chosen "replay the turn" or something. When I look at the score card I clearly don't have any clay huts.

Thanks for the help! I appreciate it. That was obviously my problem.