First you should check the dates you've chosen on the calendar.
Start date of the campaign should be included as the first date. If that is not helpful, other possible reasons can be related to the ad account connection or wrong ad account selection.
Ad account connection: Please check if the ad account used while creating this campaign appears under Assets > Accounts
Ad account filter: It may be the case that the ad account is not included in the filter on campaign list page.
Another reason why you're not able to see the campaigns might be, if you don't have admin access to all campaigns, you might not have been authorized to see the campaigns under a specific Brand or Company.
In order to manage permissions, someone with admin access needs to go to Settings > Users and find the user there, when they find the user they need to click on "Manage User Permissions" and give the user access to see the certain Brand or Company. They can choose to give permission to all brands under a Company or choose specific brands to give permission to.
Please contact your CSM if the campaign still can't be seen after you checked the possible reason listed above.