trying to install previous version. the installer will not allow and directs to new version

We generally discourage people from browsing the web with older versions of Flash Player.  Flash Player's job is to process untrusted content from the web.  Attackers can look at the binary differences between Flash versions to reverse-engineer changes, and there are tools and techniques that make this process very efficient.

If the technical support folks at this particular content provider are recommending that you revert to an old version, that's not ideal.  Please feel free to forward this thread to them.  We'd be happy to talk to them about any issues that their users are encountering to understand the problem and offer them an optimal solution (and/or better guidance for end-users).

If you want to explain what the actual problem is, we might have a more secure suggestion for a workaround...

Use the standalone uninstaller to completely remove Flash Player and revert to a previous version.

Uninstall Flash Player for Windows