Do you both have R Studio installed with dada2 already? I think I’ve seen this before and it has to do with a broken precedence for loading the R libraries. If that is the case, this issue describes a workaround. Basically you can create that .Rprofile line (in your $HOME directory) and then just delete it (or comment it out) depending on whether you are using R Studio or QIIME 2. (We’re trying to figure out how to prevent this, because we know this is a terrible workaround, things should really just work better than that.)
If you aren’t using R Studio with dada2, let us know!