Can anyone tell me if you can downgrade a software version of 30 port analog module on an Avaya IP Office 412? Customer has ordered his own module and they sent him one that has a higher software version than the one he is currently running. I'm not sure it can be done but I thought I would ask before telling him to return the module.

Any help would be appreciated

Yes, just fire up the Manager running on the same release as the 406, and do the regular File | Advanced | Upgrade, which will find the expansion module and offer to downgrade it.

Usually, the customer has the version of Manager that was used to set up the system, otherwise you'll need to download the correct bin files and change your working directory.