When dealing with Facebook advertising, you can come across a wide variety of error codes and more often that not, you might not find a resolution!

An ad set error that we discovered recently puzzled us - but it perplexed us even more when we realised that there was very little information available across the web to actually fix it.

So, our data experts got to work and we were able to resolve the issue! We thought we’d share how, just in case you have been puzzled by how to fix the fault yourselves:

If you come across the following error:

‘Invalid Optimization Sub Event for Objective: The chosen optimization sub event is not supported by this objective (#1815762)’

We’re here to demystify the resolution for you.



This error message is quite misleading and implies that there is an issue with the conversion event or optimisation within the ad set. 

We tried multiple approaches to resolve it, as the error had not occurred on previous ad sets with identical configurations across various accounts.

The error message would appear when the ad set was remade on the same or a different campaign,  so this clearly wasn’t an account-related issue.

We discovered that the problem was actually due to the tracking of a certain aspect of our audience, which we were also using across multiple ad sets with no issue. 

This turned out to be a targeting expansion method that no longer works due to recent changes to Apple’s iOS14 operating system.



Our audience definition included “Reach Potential Travelers” (our client was a hotel), but this “Optimization Sub Event” is no longer working, it seems. The simple solution was to disable this feature and the error message disappeared, allowing us to publish the ad set. 

It is not currently clear as to why this is happening, but we suspect it is due to the major changes to iOS14. The ‘Reach Potential Travelers’ delivery method tracks users that have recently visited travel websites (such as booking a hotel) and then targets the ad to them. 

Because of the huge proportion of potential customers using Apple devices, and the recent privacy changes to their operating system, this makes tracking users from these devices very difficult for Facebook. 


If you have come across any Facebook errors that you just can't find the resolution for, drop us a line and our Facebook Advertising experts will be more than happy to take a look into it for you!

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