Sync issue with Outlook 365 Calendar

[stefancvetkovic]

Hello,
Im using my .net core custom app and I am generating a webcal link (ical) for subscribing it from Outlook 365.
Initial subscription goes wel, all items are imported into Outlook365, but when I change some item in my app, it doesn't reflect to Outlook365.
Do you maybe across to same issue? Any hints what should I try? Thanks