Would it change the nuance of the context if I say "could" instead of "can" here?

Rebecca

In this particular context, you can use them interchangeably. There is a slight difference in nuance. "Can" expresses more certainty or a strong possibility, while "could" sounds more hypothetical and expresses weaker possibility, but the meaning is largely the same in general spoken English. Ex: She's not calling you? It could mean she doesn't want to talk. (The speaker isn't certain) Ex: She can be sick, that's probably why she's not calling you. (The speaker thinks this is likely)