In Data3Sixty Analyze, the 3.5.x series of releases are developmental. 3.5.x is a Generally Available, non-LTS (Long Term Support) release, and has a number of improvements in operations, performance and stability over preceding versions.
Unfortunately, it's not possible to go from 3.5. to 3.4.x, which are LTS releases. You can't go 'down' in versions even though some of the 3.4.x releases are newer. The actual installation may be successful but data flows that were exported from 3.5.x during the upgrade are tagged with the version and are not backwards compatible, so they won't work on 3.4.x / 3.2.x etc.
However, many of the same features that are on 3.5.x are available on 3.4.x, for example 3.5.1 and 3.4.3 are essentially the same in terms of features and functionality.
If you already have 3.5.x and tried upgrading to 3.4.x please raise a Support ticket and the team will be able to assist you. They will want to know roughly when you upgraded to 3.5.x. This is because Data3Sixty Analyze takes daily backups and keeps them for 20 days. So, if you upgraded less than 20 days ago, (and you were previously on 3.4.x) then we may be able to get you back to your old 3.4.x version and then upgrade to the newest 3.4.x release.
Alternatively, if you upgraded to 3.5.x more than 20 days ago, then we may be able to restore your old 3.5.x instance. For both of these options, you'll need the backup files from the system. You should be able to locate these by scanning your computer for *.LXP. Please inform the Support team of the results of the search.
NOTE: Upgrading from 3.4.3 to 3.5.0 will also not work, because 3.4.3 was released after 3.5.0