How to degrade to an elder version?

Hi, I've purchased a 3.0 Version copy about a year ago. Now it says that my SMFTP maintanace has expired and that I should buy or renew a client liscense plan. In the German translation of the liscense describtion it says that once you buy SMFTP you're not obliged to renew your liscence plan and that you can use it forever.
I wrote to the SMFTP support and received a message saying that my installed version is an upgrade version and that it is not covered by my current liscense key.
I'm not aware having upgraded my copy but it could be possible as I'm allways getting those info mails.
How can I downgrade to my liscensed version? According to the e-mail that was sent to me after I purchased SMFTP It is a 3.0 version.
Any help is much appreciated.
Best regards

I have the same problem...

I tried uninstalling, removing Registry Keys and re-installing a previous version but now Smart FTP won't run at all. It just gives a Runtime Error on startup.
I have paid for SmartFTP software but currently can't use it.
Please help!

Uninstall the new version. Install the old version. Delete the registry key.