When making a change to Office 365 objects, you may sometimes see the non-informative error message “We couldn’t save your changes. Please try again”.
One example is when using the Microsoft 365 Admin Center to add a new mail address to a shared mailbox:

This nonsense error is caused by certain attributes being authoritative in your local Active Directory.
(you can ‘try again’ all you want đ)
But to solve this problem, you need to add the new email address via the proxyAddresses attribute in your local AD.
How to Correct This Error
Fixing this error can be done in different ways.
By far, the easiest way is to use Easy365Manager. With Easy365Manager, you can manage proxyAddresses as an integrated part of user properties in Active Directory:
Easy365Manager will ensure that you enter the correct format and that the address added is unique in your organization.
You can also edit the proxyAddresses attribute directly via the Attributes tab in user properties. However, there is no sanity check of values entered in this case, which can cause hard-to-troubleshoot errors.
Easy365Manager offers a lot of benefits like removing your on-premises Exchange Server and empowering your first-level support to perform complex tasks.
As an example, watch how you can replace complex PowerShell scripting when delegating calendar access:
Summary
Managing a hybrid Office 365 environment offers a lot of complexity and challenges.
The fact that certain attributes are authoritative in your on-premises Active Directory while others are managed in Office 365 can sometimes be very confusing.
With Easy365Manager, you no longer need to speculate about attribute authority as everything is managed in the familiar interface of AD Users & Computers.
Easy365Manager introduces two new tabs to user properties that let you manage Office 365 licenses and mailboxes directly from AD user properties.
You can see a list of features here.
Easy365Manager is available as a fully functional 30-day trial; you can download it here.
The simple installation can be done in just a couple of minutes.