So participants are being redirected to Qualtrics (which can only happen if they finish) but you aren’t getting data from them?
Are credits being consumed?
Are you using CSV or database saving?
Can you see .log or .gz files for them?
Do you have a pre-Pavlovia Qualtrics with matching time stamps?
It might be worth adding a link to this thread here: Data don't save on Pavlovia Data file