Ah I’ve found the problem - it’s the new param types in 2021.1. Essentially, it sees whatever you give a Keyboard for it’s correct answer as a list, not a string. This is only a problem for experiments made in 2021.1.0 - experiments made earlier will have the old param types and so will be interpreted fine. I’ll fix this in 2021.1.1, but for your specific experiment I’m afraid you’ll have to do a bit of manual substitution - you could either remake the Keyboard components again in the next version, or open the .psyexp in notepad (or equivalent program) and replace anything like this:
<Param name="correctAns" val="space" valType="list" updates="constant"/>
with this:
<Param name="correctAns" val="space" valType="str" updates="constant"/>
(val might differ between components, but the rest should stay the same, so you can use CTRL to find them all quickly)
Sorry for the inconvenience! It’s something I missed when refactoring.