If you want to post your packaged workbook (or mock up a similar scenario using sample data) so we can look at the data sources, someone may be able to advise you on how to set up the join. However, data blending is more ideal in some scenarios. With data blending comes some limitations, like the inability to filter across data sources. So, unless a join can be created that will work for your analysis, you will need to use an action filter--OR a parameter. I believe this thread gives a good example of the latter (parameters have limitations, too, like no multi-select option built in):
And you've probably seen this, but just in case: Filtering Across Multiple Data Sources | Tableau Software
Of course, someone else may have some other awesome workaround I've never seen...
Thanks for the help! The parameter solution works perfectly since I don't require multiple selections. Appreciate the link (and yes, the other link was what got me stalled in the first place...).
Excellent, glad it is working!