The event data flow between SearchAds.com and Attribution Tool will start only after the integration set up is done correctly on both sides. That is why you can only see the attribution data after the successful integration.
If you would like to see your previous/historical attribution data before you connected your MMP with SearchAds.com, please provide us with 2 CSV files (Install & In-app event report) from your related Attribution Tool.
You can find this post on How can I download raw data from MMP? useful for this case.
Once your files are ready, please contact us to upload your previous/historical data.