Update: the Presto machine at Dundas Station is broken. When customers attempt to reload, it always gives a "transaction canceled" error, which is causing customers to believe they've done something incorrect, and caused me to believe I needed to activate the card to reload.
When I was leaving the station there were about a half dozen or so commuters trying to use the broken machine. I was able to direct them to a working machine in the station, but I'm sure there's now another large group of people struggling with this.
Metrolinx and their contractors must provide a better experience than this. We can't have rushed commuters struggling to make a broken machine work because whoever designed this thing is incapable of displaying an "out of order" message. This is absolutely ridiculous.