If you think, you are entering the right credentials on the app but it still say’s “Invalid credentials”. It most probably means your IT administrator hasn’t enabled IMAP access for your account.
The below excerpt is taken from the Documentation. Try following the steps, if you don’t find the IMAP settings option, it means your IT administrator has disabled IMAP access. You need to contact your company to allow it.
Sign in to Outlook Web App. For help, see Sign in to Outlook on the web.
On the nav bar, choose Outlook (or Mail).Or
Choose App launcher > Outlook.
On the nav bar, click Settings > Options.
Under Options, click Account > My account.
On the My account page, select Settings for POP or IMAP accessOr
Under Mail > Accounts, select POP and IMAP.
The POP, IMAP, and SMTP server name as well as other settings you may need to enter are listed on the Settings for POP or IMAP Access page under POP setting, IMAP setting, or SMTP setting.
Note: If the server settings for POP server, IMAP server, and SMTP server don’t show in the Outlook on the web options, your email account may not be set up to use POP or IMAP email programs. You need to contact the IT person who manages your email service for help.
If you need help with setting up your account, please feel free to contact us here. :)