Workato will not pick up the same trigger event more than once. For example, if your recipe is set to trigger when a new invoice is created, it will only trigger once for that particular invoice. Updating the invoice would have no effect on the recipe. However, if your recipe is set to pick up invoices when they are updated, they will be picked up, and when another change is made, they will be picked up to trigger the recipe again. If you don't make any changes, they will not be processed by your recipe.
Every recipe maintains a log of what jobs (invoices) it has already processed. Once a recipe has processed a job, it will not process it again. Therefore, new invoices which have been picked up by the recipe once will not be processed by the recipe again, even if the recipe was stopped and started. This prevents duplication.
This also means that if you were to modify a recipe after running a couple of jobs through it, the invoices that were already processed will not be picked up again. The modified recipe will process only the new invoices according to the new recipe. Even though all the invoices will show up in the same job history, some were run with the old logic and some with the new logic.
To process a job again manually, you can click on the Rerun job button. This is useful for resubmitting failed jobs or to process a job that was not processed correctly before. Here is another article on rerunning jobs.