Final answer:
A Matched Audiences campaign on LinkedIn begins serving after the uploaded audience list is populated, which takes up to 48 hours after upload, and once it matches the required list size, budget, and bid are set, and ads are approved.
Step-by-step explanation:
A Matched Audiences campaign will begin serving after the audience list that you have uploaded to your campaign manager is populated and matches the required list size. This process can take up to 48 hours for upload and processing. Once the list is activated, LinkedIn will start displaying your ads to the matched audience members. It is essential that the list meets LinkedIn's criteria, which includes having a sufficient number of matched LinkedIn members.
Furthermore, for the campaign to begin serving, you must also ensure that you have set an appropriate budget, bid, and that your ads are approved. The approval process itself can take some additional time. After addressing all these requirements, your campaign can commence serving ads to the targeted audience successfully. Always monitor the campaign performance closely after launch to make any necessary adjustments to improve results.