Office 365 has a default password policy which is applied to all users. This is a good practice but could pose some problems with the Meetio Service Account, especially if you have a policy with a short period before requiring the user to change the password.
If you want to exempt the Meetio Service Account from the default password policy it is not possible to do through Office 365 Admin portal. But, it is possible to do it through Remote Powershell against Azure Active Directory (which Office 365 is based on).
To do so you need to install Azure Active Directory Module for Windows Powershell. Do this through the PowerShell command (in an elevated command prompt):
Install-Module -Name AzureAD
Then you need to supply your credentials (you need to be Office 365 Global admin)
$AzureAdCred = Get-Credential
With them you connect to Azure Active Directory with the command
Connect-AzureAD -Credential $AzureAdCred
After that you set the password to never expire through with the command
Get-AzureADUser -Filter "userPrincipalName eq 'email@example.com'" | Set-AzureADUser -PasswordPolicies DisablePasswordExpiration