Unable to create alias on Shared Mailbox in O365 after hybrid join

Hi, 

Looking for the best practice on how to add alias, before joining to hybrid I could add alias for single or shared account in O365/Exchange online but after hybrid join, I can't see a way to add alias for shared account in O365. Each time I add alias for shared account in O365/Exchange i gets a error says  "We couldn't save your changes. Please try again."

If I would like to add alias for user account, I cannot do it via the O365/Exchange online, I have to go to local AD>User>user attribute>Proxy address> smtp:email address removed for privacy reasons that's how I can get alias for user accounts

I can create new users or shared account and add alias to them but can't do with already existed shared account. 

My environment: 

• One AD Forest with One Domain (local)
• 1 O365 Tenant with 25 domains

There isn't on-premise Exchange server. Does anyone have any suggestions on how to add an alias to shared account in o365 if we have Hybrid join.? 

Many thanks