Can not use unicode at subject line of Icloud calendar in Outlook 2013 - Outlook 2016

My note book installls windows 10, Icloud, Outlook 2013.

I use Icloud calendar in Outlook to synchronise with Iphone.

Before I could type Unicode at the subject line of Icloud calendar and everything were OK.

After I reset windows 10 and reinstall office 2013, cloud 5.2, I could not type unicode (Vietnamese) at the subject line. I event upgrade office 2013 to office 2016, but the situation is the same

If I type, for example "Chuẩn bị họp với khách hàng" (means meeting with client), then press tab button to move to the next field, It automatically converts to "Chu?n b? h?p v?i khách hàng". Some characters are converted to question mark "?".

This problem happens to subject field only. The next field, location, is OK with unicode.

There is no problem if I use unicode with Outlook calendard (PST file, not Icloud calendar in Outlook)

Please help me to solve the problem. Thank you.