Finally,I have found out the real solution.Replace

IssuerSigningKey = new X509SecurityKey(AppleRootCA),

to

IssuerSigningKey = new ECDsaSecurityKey(certificate0.GetECDsaPublicKey()),

All things will work well.

This solution helps me: https://github.com/naveenjangra2/AppStoreServerNotifications

Also,here is an example token from App Store Server Notifications I found out in Github.com:https://github.com/alexalok/AppStoreServerNotificationsV2/blob/main/AppStoreServerNotificationsV2/Converters/Sandbox_Resubscription.json

Thanks naveenjangra2 and alexalok works!