There are a couple of reasons that could influence why you aren't seeing suggestions.
For starters, the system may not find statistically significant data in any ad group to declare ads as losing ads. In such cases you can turn on the Turbo Mode to see all ad groups that have active ads.
In the Turbo Mode, the system lowers the data threshold when selecting losing ads. It may not make recommendations for ad groups that don't have enough data.
Note: Turbo mode is not available for Bing ads.
This can also happen due to the filters selected, as there might not be any ads that match the criteria. For example, if the network is set to search and ad type is set to image, there won't be any suggestions because there are no image ads on the search network in AdWords. You can read more about the filters here.
Finally, make sure to check the status of the campaigns, as the system only shows suggestions for active campaigns and ad groups.
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