In this case, the cause was a faulty or poor-fitting hot-shoe adapter connection on the Canon EOS 1300D. Replacing the adapter with a different one that fit the camera’s hot shoe more securely solved the problem and the studio flash triggered normally.

If a sync adapter works on one camera but not another, the most likely issue is often mechanical or electrical contact at the hot shoe rather than a camera setting. A loose adapter, poor center-pin contact, or an adapter that doesn’t seat properly can prevent the trigger signal from reaching the flash.