1.请确保ADM的服务器安装了Azure AD的MSOnline PowerShell模块：
MSOnline PowerShell 模块可以通过两种方式安装：
1）使用软件
通过 PowerShell cmdlet，需要满足以下前提：
i) 软件要求：
1.安装 PowerShell 3.0 及更高版本
2.下载并安装 Microsoft Online 服务登录助手。
3.为 Windows PowerShell 启用 Azure AD 模块
4.安装的是64位版本的 ADManager Plus
ii) 其他要求：
1. 用于配置的 Office 365 帐号不得启用 MFA（Multi-Factor-Authentication）。
2. 该帐户必须是Global Administrator (首选) 或者User Management Administrator
满足上述要求后，请按照以下步骤操作：单击下面的链接以下载 Azure AD 模块。
在安装了 ADManager Plus 的机器上打开 Windows PowerShell
$UserCredential = Get-Credential（输入在 ADManager Plus 中配置的凭据，在 Admin-->Office 365 下）
导入模块 MSOnline
Connect-MsolService [输入 ADManager Plus 中提供的 Office 365 凭据，如果再次出现提示]
Get-MsolDomain
然后重新启动 ADManager Plus 的服务并检查同样的问题是否仍然存在
执行上述步骤应该可以解决错误问题。
为避免翻译有歧义，另附英文原文：
We understand that you are facing an issue with the O365 connectivity. Pertaining the prompt to install MSOnline Powershell for Azure AD.
Before you set out to add an Office 365 account in ADManager Plus, ensure that you MSOnline PowerShell module for Azure Active Directory is also installed on the machine where ADManager Plus is installed.
The MSOnline PowerShell module can be installed in two ways:
Using software
Through PowerShell cmdlet
There could be few reasons why you might face errors when you are attempting to configure Office 365 accounts in your ADManager Plus.
Troubleshooting:
The error can be resolved by meeting the following requirements:
i) Software requirements:
Install PowerShell 3.0 and above
Download and install Microsoft Online services sign-in assistant.
Enable Azure AD module for Windows PowerShell
Install 64-bit version of ADManager Plus
ii) Other requirements:
1. The Office 365 account used to configure must not have the MFA (Multi-Factor-Authentication) enabled.
2. The account must be a Global Administrator (Preferred) or User Management Administrator.
Once the above requirements are met, follow the steps mentioned below: Click on the link below to download the Azure AD modules.
Open Windows PowerShell on the machine where ADManager Plus is Installed
$UserCredential = Get-Credential (Enter the credentials configured in ADManager Plus under Admin-->Office 365)
Import-Module MSOnline
Connect-MsolService [Enter the Office 365 credential given in ADManager Plus, if prompted again]
Get-MsolDomain
And then restart the service of ADManager Plus & check if the same issue persists
Performing the above steps should resolve the issue with the error.