Everything was working fine until got this Service Unavailable error from my MOSS central administration. I checked the IIS and app pool, everything seemed fine. I double checked that the domain account that ran my Central Admin app pool had sufficient rights, this was a dev server farm and people could be playing around with it. But this account had sufficient rights. Then I checked to login remotely to another server in this farm using the same domain account and I got the error that the account was locked! Now that was the problem. I checked with IT and got this account unlocked and Central Admin came back online :)
Practical notes on Microsoft 365, SharePoint Online, Entra, Azure and PowerShell - from an IT consultant who's been working with Microsoft technologies since 2004.