If the tool runs, but you get a "Request Size Limit Exceeded" error when trying to create ad groups, you might be exceeding the ad group creation limits.
The number of ad groups the AdWords API lets our system post at one time for shopping campaigns is limited. This is why when the number of ad groups being created exceeds 5000 our system shows an error.
AdWords limits for the number of ad groups that can be created in the interface is 20,000 per campaign but our system is not able to post more than 5000 ad groups at a time.
This error usually happens when trying to split by Item ID (too many ad groups to be created one by one).
Depending on the campaign structure you want to accomplish, you can use any of the other levels to split your campaign. Also, since shopping campaigns let you manage bids and performance at the product group level, creating a separate ad group for each SKU may not always be required.
For example, in instead of creating ad groups by SKU, you can group by Product Type. It'll reduce the number of ad groups you want to create, which will make easier to manage the campaign and bidding in AdWords (and Optmyzr).
If your merchant feed is linked and even then if you encounter an error, this can be because the merchant feed may have products which are pending for approval.
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