Hi - I've branched your reply off into it's own question. This will allow us to troubleshoot and answer your question. Are you deploying your app measurement file via DTM? If not, I'll move this to the Analytics community.
If you're receiving an "s is not defined" message, you're likely experiencing an scoping issue. You can read about a potential solution here - "S is not defined" Error in Adobe DTM
You could also test to see if that is the issue by removing the plug-in from the custom section and instead just write some code that references the s object. If you get a similar error, you know it's a scoping issue.
Thank you Jantzen,
That thread solved my "s is not defined" issue. Now that I've implemented the s.getValOnce() plugin, how can I use it in DTM?
Right now, I have s.prop25=s.getValOnce(s.prop25,'ibCustomer'); in a page load rule under Conditions > Custom Criteria. This is not working.
Maybe try writing a function in a data element like the one below
Then you can call that data element in the rule builder
prop 25 = %DataElementName%
I apologize for not being able to give a more concrete answer, I'm not an expert with any of the Analytics plugins.