After publishing a campaign in Display Autopilot it can happen that your wallet shows €0 balance. Why this could happen is explained below.
When publishing a campaign on Display Autopilot we make a reservation for the daily budget for the duration of your campaign. Say you have set a daily budget of €10 and your campaign is set to run for 2 days. This means we will have to make a reservation of €20.
If your wallet balance was €20 in total before, now we will deduct €20 from your balance for the campaign you just published. This will lead to a €0 wallet balance.
This does not mean your €20 is completely spent already! It's only reserved and still there! As your campaign starts running this reservation is used to pay for the clicks and views your campaign generates.
In the Transaction Overview you can see exactly what movements of funds have been made between your wallet and campaigns.
Why are we making this reservation?
We are making this reservation to prevent double spending. The campaigns you publish and the daily budget you give to those campaigns are committed to the ad serving network, telling them they are allowed to spend the entire daily budget (per day of course). If we wouldn't make this reservation, theoretically you could set up multiple campaigns leading to an overspend which can't be covered by your wallet balance, leading to a negative wallet balance. This would be very inconvenient to you and therefore we have implemented the reservation upon publishing a campaign.
If you want to publish multiple campaigns, just make sure to have a sufficient balance in your wallet and you should be fine!
Important side note about the counting of days
The day you publish your campaign will be counted as the first day until midnight Central European Time. Any day afterwards will count as an extra day. This could mean that in the above example your first €10 will be spent much faster as the day has already progressed. All other following days will spread out the daily budget over a 24 hour period.