When using the designer program, click Open to show the list of specification files in the same directory as your Payables accounting data - this screen also lists the respective spec Titles. Check from here if there are any duplicated or similar titles.

Perhaps try (temporarily) removing all of the sample spec files to a different directory, so that they don't get in the way. Spec files start with AP$ and have a data extenstion that matches your accounting data.

Ensure that your spec that you modified has a file name that starts with AP$ and that the file extension is the same as the other data files.

Ensure that your spec is saved in the same directory as your Payables accounting data or it will not be loaded.