How to Fix: After upgrading WHMCS: Down for Maintenance An upgrade is currently in progress

I recently came across an issue I’d not seen before. After performing what I thought was a proper upgrade, I found that my support and sales portal was displaying the error:

Down for Maintenance (Err 2)
An upgrade is currently in progress… Please come back soon…

I found several difference references to this error on the web. The one detail that I was able to glean was that this error usually occurs when the files are updated, but the database is not. This was the case in my situation. It turns out that I caused my own problem. The key to the mystery is that the files to perform the database upgrade are actually part of the “install” directory.

The instructions for a full upgrade are  here: http://docs.whmcs.com/Upgrading

Basically  you just:

1. Extract the files
2. Rename the admin and cron directories as needed
3. Copy those files over the existing installation
4. Visit the site and follow the upgrade instructions, if any.

My problem was that #4  includes an error at the end that tells you the install directory still exists, delete it.  Being a guy who likes to optimize a process as much as possible, I was deleting the install directory before copying  in the files.  This process worked great 99% of the time.  However, eventually they changed the database structure from 5.2.13 to 5.2.14 or 5.2.15.  THEN the result was that the WHMCS software could not upgrade the database. and I got the wonderful WHMCS Down for Maintenance error.

So really the steps should be:

1. Extract the files
2. Rename the admin and cron directories as needed
3. Copy those files over the existing installation
4. Visit the site and follow the upgrade instructions, if any.
5. Delete the install directory when prompted.

At that point, everything should work fine.   At least it did for my particular incarnation of the problem.  I hope it solves your issues too.