How to fix “App Store Connect Operation ERROR ITMS-90771”

Add this in your info.plist and then resubmit your app

<key>BGTaskSchedulerPermittedIdentifiers</key>
<array>
    <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
</array>

or if you use more than one BGTask then use this code

<key>BGTaskSchedulerPermittedIdentifiers</key>
<array>
    <string>com.yourCompanyName.appName1</string>
    <string>com.yourCompanyName.appName2</string>
</array>