Just downloaded and started a new game - with iron bars in inventory click upgrade power tower - takes the iron but doesn't upgrade.
Update 2/27 - started a new game and was able to upgrade the tower early on. After playing for about 3 hours, tried to upgrade to steel level, and ran into the same glitch - takes the bars from inv, says it upgrades the tower, but the tower GUI doesn't advance and the melted snow circle doesn't enlarge.
Another unrelated issue - instead of "breaking" the pickaxes just disappear, sometimes quickly - made a new steel pickaxe - mined 1 strongium node, axe was gone.